CoAP Component

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An easy-to-use CoAP client and server implementation.

Syntax

nsoftware.IPWorksIoT.Coap

Remarks

The CoAP component provides a lightweight, fully-featured CoAP client and server implementation.

Using the Component in Client Mode

While in client mode (i.e., the Listening property is disabled; its default setting), the component can be used to send requests to a CoAP server. It can also be used to register as an observer for various server-side resources, causing the server to send notifications anytime said resources change.

To send a request, populate the RequestData, RequestContentFormat, RequestETag, and RequestOptions properties (if necessary, and as applicable), then call one of the following methods:

• Get
• Post
• Put
• Delete
• SendCustomRequest

The methods above require a URI as a parameter. The format of the URI parameter is coap://hostname:port/resource. The port is optional, and if not specified will default to 5683. For instance coap://myserver/test and coap://myserver:5683/test are equivalent.

Once a response is received, the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties will be populated, and the RequestComplete event will fire. (If the request times out, the properties are not populated, but the event still fires.) coap.OnRequestComplete += (s, e) => { Console.WriteLine("Request complete!"); Console.WriteLine(coap.ResponseCode); }; // Make a GET request to download a picture. coap.Get("coap://mycoapserver/pictures/animals/cats4.dat?format=png"); // Imaginary function which accepts PNG image data and displays the picture to the user. showPicture(coap.ResponseDataB);

To observe a resource, call the StartObserving method. Assuming the server accepts the observer registration request, it will begin sending notifications for the resource anytime it changes. Each change notification will cause the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties to be populated, and the Notification event to fire.

To stop observing a resource, either call StopObserving with the same URI value used to call StartObserving, or set the Notification event's StopObserving parameter to True. coap.OnNotification += (s, e) => { // Notifications can arrive out of order; only print to the log if this is the latest one we've received. if (e.IsLatest) { Console.WriteLine("Received notification for the resource at: " + e.URI); Console.WriteLine("New Value: " + coap.ResponseData); } } // Start observing a temperature sensor's data. Assume temperature values are sent back in text format. coap.StartObserving("coap://mycoapserver/home/living_room/sensors/temperature?unit=fahrenheit"); // Assume the server accepts the request and starts sending notifications every so often. // ... // Later, stop observing the resource. coap.StopObserving("coap://mycoapserver/home/living_room/sensors/temperature?unit=fahrenheit");

Using the Component in Server Mode

To operate in server mode, set the LocalPort to the port the component should listen on (typically 5683, the standard CoAP port), then enable the Listening property. Each time a request arrives, the RequestData, RequestContentFormat, RequestETag, and RequestOptions properties will be populated, and the Request event will fire.

A response can be sent by populating the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties as desired before the event finishes. Alternatively, the Request event's SendResponse parameter can be set to False in order to send a response back later. In this case, the RequestId value from the event should be used to call the SendResponse method later. coap.OnRequest += (s, e) => { // For the purpose of this snippet, assume we only service GET requests, which have a method code of 1. if (e.Method == 1) { Console.WriteLine("GET request received for URI path: " + e.URIPath + " and URI query params: " + e.URIQuery); coap.ResponseCode = "2.05"; // "Content". // Imaginary methods that look up the data and content format of the resource based on the URI path and URI query parameters. coap.ResponseData = lookupResourceData(e.URIPath, e.URIQuery); coap.ResponseContentFormat = lookupResourceContentFormat(e.URIPath, e.URIQuery); } else { coap.ResponseCode = "4.05"; // "Method Not Allowed". coap.ResponseData = "Only GET requests are allowed."; // Include a diagnostic payload. coap.ResponseContentFormat = ""; } // Alternatively, this event could simply save the e.RequestId value somewhere, then some other code could fill in the Response* // properties and call the SendResponse() method later. }; coap.OnResponseComplete += (s, e) => { Console.WriteLine("Response sent for request with Id " + e.RequestId); };

In server mode, the component can also support resource observation. When a client attempts to register itself as an observer of a resource, the Register event will fire; setting this event's Accept parameter to True will cause the component to accept the registration.

To notify clients that a resource has changed, populate the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties as desired, and then call the SendNotification method, passing it the URI of a resource that has registered observers.

When a client has unregistered from further change notifications, the Unregistered event will fire. coap.OnRegister += (s, e) => { Console.WriteLine("Client " + e.RemoteHost + ":" + e.RemotePort + " has registered for notifications for the URI " + e.URI); // Imaginary method that helps ensure the application keeps track of observed URIs. The component itself maintains the // list of observers for each URI, so the application just needs to know that there are observers in the first place. observerRegisteredForURI(e.URI); e.Accept = true; }; coap.OnUnregistered += (s, e) => { Console.WriteLine("Client " + e.RemoteHost + ":" + e.RemotePort + " has unregistered from notifications for the URI " + e.URI); // As above, imaginary method that helps ensure the application keeps track of observed URIs. observerUnregisteredForURI(e.URI); }; // Somewhere else in the application, this sort of code might get called after a resource changes to inform any observers of // the change. We use another imaginary method here to check if the changed resource is observed, and to get its information. if (isResourceObserved()) { coap.ResponseCode = "2.05"; // "Content". coap.ResponseDataB = getResourceContent(); coap.ResponseContentFormat = getResourceContentFormat(); coap.SendNotification(getResourceURI()); }

Property List

The following is the full list of the properties of the component with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the component with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the component with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the component with short descriptions. Click on the links for further details.

Listening Property (CoAP Component)

Whether the component should operate in server mode by listening for incoming requests.

Syntax

• C#
• VB.NET

public bool Listening { get; set; }

Public Property Listening As Boolean

Default Value

False

Remarks

This property indicates whether the component operates in server mode or client mode.

When this property is false (default), the component operate in client mode, allowing applications to send requests using the Get, Post, SendCustomRequest, etc. methods.

When this property is true, the component listens on LocalPort for incoming CoAP requests, firing the Request event anytime one arrives. Applications can service these requests directly during Request events, or send separate responses later using the SendResponse method.

Applications that wish to use the component in server mode should set the LocalPort property to the desired listening port (such as 5683, the standard CoAP port) before calling StartListening. Otherwise the system will choose a port at random.

Note: Use the StartListening and StopListening methods to control whether the component is listening.

This property is not available at design time.

LocalHost Property (CoAP Component)

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

• C#
• VB.NET

public string LocalHost { get; set; }

Public Property LocalHost As String

Default Value

""

Remarks

The LocalHost property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multi-homed hosts (machines with more than one IP interface).

NOTE: LocalHost is not persistent. You must always set it in code, and never in the property window.

LocalPort Property (CoAP Component)

The UDP port in the local host where UDP binds.

Syntax

• C#
• VB.NET

public int LocalPort { get; set; }

Public Property LocalPort As Integer

Default Value

0

Remarks

The LocalPort property must be set before UDP is activated (Active is set to True). It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting it to 0 (default) enables the TCP/IP stack to choose a port at random. The chosen port will be shown by the LocalPort property after the connection is established.

LocalPort cannot be changed once the component is Active. Any attempt to set the LocalPort property when the component is Active will generate an error.

The LocalPort property is useful when trying to connect to services that require a trusted port in the client side.

PendingRequests Property (CoAP Component)

Collection of pending requests.

Syntax

• C#
• VB.NET

public CoAPRequestMap PendingRequests { get; }

Public ReadOnly Property PendingRequests As CoAPRequestMap

Remarks

This collection property holds a list of CoAPRequest items.

When the component is operating in client mode (i.e., the Listening property is disabled), each item represents an outgoing request for which a response has not yet been received.

When the component is operating in server mode (i.e., the Listening property is enabled), each item represents an incoming request for which a response has not yet been sent.

This property is read-only and not available at design time.

RequestContentFormat Property (CoAP Component)

The request content format.

Syntax

• C#
• VB.NET

public int RequestContentFormat { get; set; }

Public Property RequestContentFormat As Integer

Default Value

-1

Remarks

When the component is operating in client mode (i.e., the Listening property is disabled), this property specifies the content format that should be included in outgoing requests.

When the component is operating in server mode (i.e., the Listening property is enabled), this property is populated with the content format included in incoming requests (if any) anytime the Request event fires.

In either case, the valid set of values for this property is -1, or a value in the range 0 to 65535. -1 prevents a Content-Format option from being included when sending a request, or indicates that one was not included in a received response.

The following table provides a (non-exhaustive) list of some of the more common content formats; refer to the IANA's CoAP Content-Formats registry for a full list.

This property is not available at design time.

RequestData Property (CoAP Component)

The request data.

Syntax

• C#
• VB.NET

public string RequestData { get; set; }
public byte[] RequestDataB { get; set; }

Public Property RequestData As String
Public Property RequestDataB As Byte()

Default Value

""

Remarks

When the component is operating in client mode (i.e., the Listening property is disabled), this property specifies the data that should be included in requests sent using Post, Put, or SendCustomRequest.

When the component is operating in server mode (i.e., the Listening property is enabled), this property is populated with the data included in incoming requests (if any) anytime the Request event fires.

This property is not available at design time.

RequestETag Property (CoAP Component)

The request ETag.

Syntax

• C#
• VB.NET

public string RequestETag { get; set; }
public byte[] RequestETagB { get; set; }

Public Property RequestETag As String
Public Property RequestETagB As Byte()

Default Value

""

Remarks

When the component is operating in client mode (i.e., the Listening property is disabled), this property specifies the ETag that should be included in outgoing requests. Leave it empty to prevent an Etag option from being included.

When the component is operating in server mode (i.e., the Listening property is enabled), this property is populated with the ETag included in incoming requests (if any) anytime the Request event fires. It will be empty if an Etag option was not included.

This property is not available at design time.

RequestOptions Property (CoAP Component)

Collection of request options.

Syntax

• C#
• VB.NET

public CoAPOptionList RequestOptions { get; }

Public Property RequestOptions As CoAPOptionList

Remarks

This collection property holds a list of CoAPOption items.

When the component is operating in client mode (i.e., the Listening property is disabled), each item represents an option that will be included in the next outgoing request.

When the component is operating in server mode (i.e., the Listening property is enabled), each item represents an option included in the most-recently-received request.

This property is not available at design time.

ResponseCode Property (CoAP Component)

The response code.

Syntax

• C#
• VB.NET

public string ResponseCode { get; set; }

Public Property ResponseCode As String

Default Value

""

Remarks

When the component is operating in client mode (i.e., the Listening property is disabled), this property is populated with the response code included in incoming responses anytime the RequestComplete event fires.

When the component is operating in server mode (i.e., the Listening property is enabled), this property specifies the response code that should be included in outgoing responses (regardless of whether they are sent immediately after Request fires, or later using SendResponse or SendNotification).

In either case, the valid set of values for this property are strings of the format c.dd, where c is a class value in the range 2 to 7, and dd is a detail value in the range 00 to 31.

The following table provides a (non-exhaustive) list of some of the more common response codes; refer to the IANA's CoAP Response Codes registry for a full list.

This property is not available at design time.

ResponseContentFormat Property (CoAP Component)

The response content format.

Syntax

• C#
• VB.NET

public int ResponseContentFormat { get; set; }

Public Property ResponseContentFormat As Integer

Default Value

-1

Remarks

When the component is operating in client mode (i.e., the Listening property is disabled), this property is populated with the content format included in incoming responses anytime the RequestComplete event fires.

When the component is operating in server mode (i.e., the Listening property is enabled), this property specifies the content format that should be included in outgoing responses (regardless of whether they are sent immediately after Request fires, or later using SendResponse or SendNotification).

In either case, the valid set of values for this property is -1, or a value in the range 0 to 65535. -1 prevents a Content-Format option from being included when sending a response, or indicates that one was not included in a received response.

The following table provides a (non-exhaustive) list of some of the more common content formats; refer to the IANA's CoAP Content-Formats registry for a full list.

This property is not available at design time.

ResponseData Property (CoAP Component)

The response data.

Syntax

• C#
• VB.NET

public string ResponseData { get; set; }
public byte[] ResponseDataB { get; set; }

Public Property ResponseData As String
Public Property ResponseDataB As Byte()

Default Value

""

Remarks

When the component is operating in client mode (i.e., the Listening property is disabled), this property is populated with the data included in incoming responses (if any) anytime the RequestComplete event fires.

When the component is operating in server mode (i.e., the Listening property is enabled), this property specifies the data that should be included in outgoing responses (regardless of whether they are sent immediately after Request fires, or later using SendResponse or SendNotification).

This property is not available at design time.

ResponseETag Property (CoAP Component)

The response ETag.

Syntax

• C#
• VB.NET

public string ResponseETag { get; set; }
public byte[] ResponseETagB { get; set; }

Public Property ResponseETag As String
Public Property ResponseETagB As Byte()

Default Value

""

Remarks

When the component is operating in client mode (i.e., the Listening property is disabled), this property is populated with the ETag included in incoming responses (if any) anytime the RequestComplete event fires. It will be empty if an Etag option was not included.

When the component is operating in server mode (i.e., the Listening property is enabled), this property specifies the ETag that should be included in outgoing responses (regardless of whether they are sent immediately after Request fires, or later using SendResponse or SendNotification). Leave it empty to prevent an Etag option from being included.

This property is not available at design time.

ResponseOptions Property (CoAP Component)

Collection of response options.

Syntax

• C#
• VB.NET

public CoAPOptionList ResponseOptions { get; }

Public Property ResponseOptions As CoAPOptionList

Remarks

This collection property holds a list of CoAPOption items.

When the component is operating in client mode (i.e., the Listening property is disabled), each item represents an option included in the most-recently-received response.

When the component is operating in server mode (i.e., the Listening property is enabled), each item represents an option that will be included in the next outgoing response.

This property is not available at design time.

Timeout Property (CoAP Component)

A timeout for the component.

Syntax

• C#
• VB.NET

public int Timeout { get; set; }

Public Property Timeout As Integer

Default Value

60

Remarks

This property specifies the number of seconds that the component should wait, synchronously, for a response to be received. A value of 0 means that the component will send the request data (when operating in client mode) or the response data (when operating in server mode) asynchronously, and then wait indefinitely, firing the applicable event once complete.

The component will use DoEvents to enter an efficient wait loop during any potential waiting period, ensuring that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If Timeout expires, and the response has not yet been received, the component throws an exception.

UseConfirmableMessages Property (CoAP Component)

Whether to use confirmable message.

Syntax

• C#
• VB.NET

public bool UseConfirmableMessages { get; set; }

Public Property UseConfirmableMessages As Boolean

Default Value

True

Remarks

This property specifies whether the component should send requests (if operating in client mode; i.e., when the Listening property is disabled) or responses (if operating in server mode; i.e., when the Listening property is enabled) using confirmable messages instead of unconfirmable messages.

Using confirmable messages increases reliability, since the component will automatically retransmit a message until it receives a confirmation from the remote host that the message was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the retransmission process.

Using non-confirmable messages reduces the amount of network traffic, but at the cost of reliability, since the component has no way to know whether a given message was received by the remote host, or lost in transit.

CancelRequest Method (CoAP Component)

Cancels a pending request.

Syntax

• C#
• VB.NET

public void CancelRequest(string requestId);

Async Version
public async Task CancelRequest(string requestId);
public async Task CancelRequest(string requestId, CancellationToken cancellationToken);

Public Sub CancelRequest(ByVal RequestId As String)

Async Version
Public Sub CancelRequest(ByVal RequestId As String) As Task
Public Sub CancelRequest(ByVal RequestId As String, cancellationToken As CancellationToken) As Task

Remarks

This method cancels the request in the PendingRequests collection identified by RequestId.

When the component is operating in client mode, the requests in the PendingRequests collection represent outgoing requests for which responses have not yet been received. Canceling one will cause the RequestComplete event to fire with an appropriate ErrorCode and ErrorDescription.

When the component is operating in server mode, the requests in the PendingRequests collection represent incoming requests for which responses have not yet been sent. Canceling one will cause the ResponseComplete event to fire with an appropriate ErrorCode and ErrorDescription.

Config Method (CoAP Component)

Sets or retrieves a configuration setting.

Syntax

• C#
• VB.NET

public string Config(string configurationString);

Async Version
public async Task<string> Config(string configurationString);
public async Task<string> Config(string configurationString, CancellationToken cancellationToken);

Public Function Config(ByVal ConfigurationString As String) As String

Async Version
Public Function Config(ByVal ConfigurationString As String) As Task(Of String)
Public Function Config(ByVal ConfigurationString As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

Config is a generic method available in every component. It is used to set and retrieve configuration settings for the component.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Delete Method (CoAP Component)

Sends a DELETE request to the server.

Syntax

• C#
• VB.NET

public string Delete(string URI);

Async Version
public async Task<string> Delete(string URI);
public async Task<string> Delete(string URI, CancellationToken cancellationToken);

Public Function Delete(ByVal URI As String) As String

Async Version
Public Function Delete(ByVal URI As String) As Task(Of String)
Public Function Delete(ByVal URI As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

This method sends the server a DELETE request for the resource identified by URI. If the RequestETag property is non-empty, its value will be used to include an Etag option in the request. Any additional options present in the RequestOptions collection will be included as well.

The format of the URI parameter is coap://hostname:port/resource. The port is optional, and if not specified will default to 5683. For instance coap://myserver/test and coap://myserver:5683/test are equivalent.

If the UseConfirmableMessages property is enabled when this method is called, the component will automatically retransmit the request message (if necessary) until it receives confirmation from the server that it was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the request.

If the Timeout property is greater than 0, this method will block until either a response is received, the specified timeout interval elapses, or (if UseConfirmableMessages is enabled) the retransmission period elapses; whichever occurs first. It will then return empty string.

If the Timeout property is 0, a record of the request will be added to the PendingRequests collection, and this method will finish immediately, returning an Id for the request. Passing this Id to the CancelRequest method will cancel the request (assuming it is still pending at that time).

Once a response is received, or the request times out, the component will do the following:

• Populate the Response* properties (unless the request timed out).
• Remove the request record from the PendingRequests collection, if necessary.
• Fire the RequestComplete event.

Note: This method can only be called when the component is operating in client mode (i.e., when the Listening property is disabled).

DoEvents Method (CoAP Component)

Processes events from the internal message queue.

Syntax

• C#
• VB.NET

public void DoEvents();

Async Version
public async Task DoEvents();
public async Task DoEvents(CancellationToken cancellationToken);

Public Sub DoEvents()

Async Version
Public Sub DoEvents() As Task
Public Sub DoEvents(cancellationToken As CancellationToken) As Task

Remarks

When DoEvents is called, the component processes any available events. If no events are available, it waits for a preset period of time, and then returns.

Get Method (CoAP Component)

Sends a GET request to the server.

Syntax

• C#
• VB.NET

public string Get(string URI);

Async Version
public async Task<string> Get(string URI);
public async Task<string> Get(string URI, CancellationToken cancellationToken);

Public Function Get(ByVal URI As String) As String

Async Version
Public Function Get(ByVal URI As String) As Task(Of String)
Public Function Get(ByVal URI As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

This method sends the server a GET request for the resource identified by URI. If the RequestETag property is non-empty, its value will be used to include an Etag option in the request. Any additional options present in the RequestOptions collection will be included as well.

The format of the URI parameter is coap://hostname:port/resource. The port is optional, and if not specified will default to 5683. For instance coap://myserver/test and coap://myserver:5683/test are equivalent.

If the UseConfirmableMessages property is enabled when this method is called, the component will automatically retransmit the request message (if necessary) until it receives confirmation from the server that it was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the request.

If the Timeout property is greater than 0, this method will block until either a response is received, the specified timeout interval elapses, or (if UseConfirmableMessages is enabled) the retransmission period elapses; whichever occurs first. It will then return empty string.

If the Timeout property is 0, a record of the request will be added to the PendingRequests collection, and this method will finish immediately, returning an Id for the request. Passing this Id to the CancelRequest method will cancel the request (assuming it is still pending at that time).

Once a response is received, or the request times out, the component will do the following:

• Populate the Response* properties (unless the request timed out).
• Remove the request record from the PendingRequests collection, if necessary.
• Fire the RequestComplete event.

Note: This method can only be called when the component is operating in client mode (i.e., when the Listening property is disabled).

Post Method (CoAP Component)

Sends a POST request to the server.

Syntax

• C#
• VB.NET

public string Post(string URI);

Async Version
public async Task<string> Post(string URI);
public async Task<string> Post(string URI, CancellationToken cancellationToken);

Public Function Post(ByVal URI As String) As String

Async Version
Public Function Post(ByVal URI As String) As Task(Of String)
Public Function Post(ByVal URI As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

This method sends the server a POST request for the resource identified by URI. The RequestData property specifies the data that will be sent in the request. If the RequestContentFormat and/or RequestETag properties are non-empty, their values will be used to include Content-Format and Etag options in the request (respectively). Any additional options present in the RequestOptions collection will be included as well.

The format of the URI parameter is coap://hostname:port/resource. The port is optional, and if not specified will default to 5683. For instance coap://myserver/test and coap://myserver:5683/test are equivalent.

If the UseConfirmableMessages property is enabled when this method is called, the component will automatically retransmit the request message (if necessary) until it receives confirmation from the server that it was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the request.

If the Timeout property is greater than 0, this method will block until either a response is received, the specified timeout interval elapses, or (if UseConfirmableMessages is enabled) the retransmission period elapses; whichever occurs first. It will then return empty string.

If the Timeout property is 0, a record of the request will be added to the PendingRequests collection, and this method will finish immediately, returning an Id for the request. Passing this Id to the CancelRequest method will cancel the request (assuming it is still pending at that time).

Once a response is received, or the request times out, the component will do the following:

• Populate the Response* properties (unless the request timed out).
• Remove the request record from the PendingRequests collection, if necessary.
• Fire the RequestComplete event.

Note: This method can only be called when the component is operating in client mode (i.e., when the Listening property is disabled).

Put Method (CoAP Component)

Sends a PUT request to the server.

Syntax

• C#
• VB.NET

public string Put(string URI);

Async Version
public async Task<string> Put(string URI);
public async Task<string> Put(string URI, CancellationToken cancellationToken);

Public Function Put(ByVal URI As String) As String

Async Version
Public Function Put(ByVal URI As String) As Task(Of String)
Public Function Put(ByVal URI As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

This method sends the server a PUT request for the resource identified by URI. The RequestData property specifies the data that will be sent in the request. If the RequestContentFormat and/or RequestETag properties are non-empty, their values will be used to include Content-Format and Etag options in the request (respectively). Any additional options present in the RequestOptions collection will be included as well.

The format of the URI parameter is coap://hostname:port/resource. The port is optional, and if not specified will default to 5683. For instance coap://myserver/test and coap://myserver:5683/test are equivalent.

If the UseConfirmableMessages property is enabled when this method is called, the component will automatically retransmit the request message (if necessary) until it receives confirmation from the server that it was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the request.

If the Timeout property is greater than 0, this method will block until either a response is received, the specified timeout interval elapses, or (if UseConfirmableMessages is enabled) the retransmission period elapses; whichever occurs first. It will then return empty string.

If the Timeout property is 0, a record of the request will be added to the PendingRequests collection, and this method will finish immediately, returning an Id for the request. Passing this Id to the CancelRequest method will cancel the request (assuming it is still pending at that time).

Once a response is received, or the request times out, the component will do the following:

• Populate the Response* properties (unless the request timed out).
• Remove the request record from the PendingRequests collection, if necessary.
• Fire the RequestComplete event.

Note: This method can only be called when the component is operating in client mode (i.e., when the Listening property is disabled).

Reset Method (CoAP Component)

Reset the component.

Syntax

• C#
• VB.NET

public void Reset();

Async Version
public async Task Reset();
public async Task Reset(CancellationToken cancellationToken);

Public Sub Reset()

Async Version
Public Sub Reset() As Task
Public Sub Reset(cancellationToken As CancellationToken) As Task

Remarks

This method will reset the component's properties to their default values.

SendCustomRequest Method (CoAP Component)

Sends a custom request to the server.

Syntax

• C#
• VB.NET

public string SendCustomRequest(string URI, int method);

Async Version
public async Task<string> SendCustomRequest(string URI, int method);
public async Task<string> SendCustomRequest(string URI, int method, CancellationToken cancellationToken);

Public Function SendCustomRequest(ByVal URI As String, ByVal Method As Integer) As String

Async Version
Public Function SendCustomRequest(ByVal URI As String, ByVal Method As Integer) As Task(Of String)
Public Function SendCustomRequest(ByVal URI As String, ByVal Method As Integer, cancellationToken As CancellationToken) As Task(Of String)

Remarks

This method sends the server a custom request for the resource identified by URI. The Method parameter specifies the request's method code. The following table provides a (non-exhaustive) list of some of the more common method codes; refer to the IANA's CoAP Method Codes registry for a full list.

The RequestData property specifies the data that will be sent in the request. If the RequestContentFormat and/or RequestETag properties are non-empty, their values will be used to include Content-Format and Etag options in the request (respectively). Any additional options present in the RequestOptions collection will be included as well.

The format of the URI parameter is coap://hostname:port/resource. The port is optional, and if not specified will default to 5683. For instance coap://myserver/test and coap://myserver:5683/test are equivalent.

If the UseConfirmableMessages property is enabled when this method is called, the component will automatically retransmit the request message (if necessary) until it receives confirmation from the server that it was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the request.

If the Timeout property is greater than 0, this method will block until either a response is received, the specified timeout interval elapses, or (if UseConfirmableMessages is enabled) the retransmission period elapses; whichever occurs first. It will then return empty string.

If the Timeout property is 0, a record of the request will be added to the PendingRequests collection, and this method will finish immediately, returning an Id for the request. Passing this Id to the CancelRequest method will cancel the request (assuming it is still pending at that time).

Once a response is received, or the request times out, the component will do the following:

• Populate the Response* properties (unless the request timed out).
• Remove the request record from the PendingRequests collection, if necessary.
• Fire the RequestComplete event.

Note: This method can only be called when the component is operating in client mode (i.e., when the Listening property is disabled).

SendNotification Method (CoAP Component)

Sends a notification to all clients observing a given resource.

Syntax

• C#
• VB.NET

public void SendNotification(string URI);

Async Version
public async Task SendNotification(string URI);
public async Task SendNotification(string URI, CancellationToken cancellationToken);

Public Sub SendNotification(ByVal URI As String)

Async Version
Public Sub SendNotification(ByVal URI As String) As Task
Public Sub SendNotification(ByVal URI As String, cancellationToken As CancellationToken) As Task

Remarks

This method sends a notification to all clients observing the resource identified by URI, notifying them of its latest state. Clients should be notified whenever a resource's content changes (or periodically, if it changes very often) by sending a 2.xx response code; typically 2.03 "Valid" or 2.05 "Content". Clients should also be notified if a resource can no longer be observed (e.g., when it is deleted) by sending a notification with a non-2.xx response code (e.g., 4.04 "Not Found"). The component will automatically unregister all observers when a non-2.xx notification is sent.

The ResponseData property specifies the data that will be sent in the response, and the ResponseCode property specifies the response code. If the ResponseContentFormat and/or ResponseETag properties are non-empty, their values will be used to include Content-Format and Etag options in the response (respectively). Any additional options present in the ResponseOptions collection will be included as well.

If the UseConfirmableMessages property is enabled when this method is called, the component will automatically retransmit the response message (if necessary) until it receives confirmation from the client that it was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the response.

Note: This method can only be called when the component is operating in server mode (i.e., when the Listening property is enabled).

SendResponse Method (CoAP Component)

Sends a response for a given pending request to the corresponding client.

Syntax

• C#
• VB.NET

public void SendResponse(string requestId);

Async Version
public async Task SendResponse(string requestId);
public async Task SendResponse(string requestId, CancellationToken cancellationToken);

Public Sub SendResponse(ByVal RequestId As String)

Async Version
Public Sub SendResponse(ByVal RequestId As String) As Task
Public Sub SendResponse(ByVal RequestId As String, cancellationToken As CancellationToken) As Task

Remarks

This method sends a response for the request in the PendingRequests collection identified by RequestId. The ResponseData property specifies the data that will be sent in the response, and the ResponseCode property specifies the response code. If the ResponseContentFormat and/or ResponseETag properties are non-empty, their values will be used to include Content-Format and Etag options in the response (respectively). Any additional options present in the ResponseOptions collection will be included as well.

If the UseConfirmableMessages property is enabled when this method is called, the component will automatically retransmit the response message (if necessary) until it receives confirmation from the client that it was received. Note that the retransmission period is not infinite; eventually the component will assume that the message is undeliverable and time out the response. The ResponseComplete event will fire once the message receipt is confirmed (or once the retransmission period elapses).

If the UseConfirmableMessages property is disabled, the ResponseComplete event will fire immediately instead, since there is no way to know whether the client received the response.

Note: This method can only be called when the component is operating in server mode (i.e., when the Listening property is enabled).

StartListening Method (CoAP Component)

This method starts listening for incoming connections.

Syntax

• C#
• VB.NET

public void StartListening();

Async Version
public async Task StartListening();
public async Task StartListening(CancellationToken cancellationToken);

Public Sub StartListening()

Async Version
Public Sub StartListening() As Task
Public Sub StartListening(cancellationToken As CancellationToken) As Task

Remarks

This method begins listening for incoming connections on the port specified by LocalPort. Once listening, events will fire as new clients connect and data are transferred.

To stop listening for new connections, call StopListening. To stop listening for new connections and to disconnect all existing clients, call Shutdown.

StartObserving Method (CoAP Component)

Registers the component as an observer for a given resource.

Syntax

• C#
• VB.NET

public string StartObserving(string URI);

Async Version
public async Task<string> StartObserving(string URI);
public async Task<string> StartObserving(string URI, CancellationToken cancellationToken);

Public Function StartObserving(ByVal URI As String) As String

Async Version
Public Function StartObserving(ByVal URI As String) As Task(Of String)
Public Function StartObserving(ByVal URI As String, cancellationToken As CancellationToken) As Task(Of String)

Remarks

This method registers the component as an observer for the resource identified by URI. If the server accepts the registration, then it will periodically notify the component about any changes to the specified resource. These "change notifications" are exposed via the Notification event.

This method operates in the exact same manner as the Get method, with the exception of the two things listed below. Refer to the Get method's documentation for more information.

1. When constructing the request, the component automatically includes an Observe option. The presence of this option is what indicates to the server that the component wishes to register itself as an observer for the specified resource.
2. When the server receives the request, its response causes the Notification event to fire instead of the RequestComplete event. (Unless it decides to reject the registration, in which case it will handle the request just like a normal GET request, and the RequestComplete event will fire when its response is received, just like it would if Get had been called.)

Once the component has successfully registered itself as an observer, the server will continue to deliver change notifications for the specified resource until the component unregisters, or the resource can no longer be observed (e.g., if it is deleted). To unregister, either call the StopObserving method with the same URI value, or set the Notification event's StopObserving parameter to True.

Note: This method can only be called when the component is operating in client mode (i.e., when the Listening property is disabled).

StopListening Method (CoAP Component)

This method stops listening for new connections.

Syntax

• C#
• VB.NET

public void StopListening();

Async Version
public async Task StopListening();
public async Task StopListening(CancellationToken cancellationToken);

Public Sub StopListening()

Async Version
Public Sub StopListening() As Task
Public Sub StopListening(cancellationToken As CancellationToken) As Task

Remarks

This method stops listening for new connections. After being called, any new connection attempts will be rejected. Calling this method does not disconnect existing connections.

To stop listening and to disconnect all existing clients, call Shutdown instead.

StopObserving Method (CoAP Component)

Unregisters the component as an observer for a given resource.

Syntax

• C#
• VB.NET

public void StopObserving(string URI);

Async Version
public async Task StopObserving(string URI);
public async Task StopObserving(string URI, CancellationToken cancellationToken);

Public Sub StopObserving(ByVal URI As String)

Async Version
Public Sub StopObserving(ByVal URI As String) As Task
Public Sub StopObserving(ByVal URI As String, cancellationToken As CancellationToken) As Task

Remarks

This method unregisters the component as an observer for the resource identified by URI. This method operates in the exact same manner as the Get method, with the exception of the two things below; refer to the Get method's documentation for more information:

1. When constructing the request, the component automatically includes an Observe option with a value of 1. The presence of this option indicates to the server that the component wishes to unregister from further change notifications.
2. This method, unlike Get, does not return a request Id.

Note: This method can only be called when the component is operating in client mode (i.e., when the Listening property is disabled).

Error Event (CoAP Component)

Information about errors during data delivery.

Syntax

• C#
• VB.NET

public event OnErrorHandler OnError;

public delegate void OnErrorHandler(object sender, CoapErrorEventArgs e);

public class CoapErrorEventArgs : EventArgs {
  public int ErrorCode { get; }
  public string Description { get; }
}

Public Event OnError As OnErrorHandler

Public Delegate Sub OnErrorHandler(sender As Object, e As CoapErrorEventArgs)

Public Class CoapErrorEventArgs Inherits EventArgs
  Public ReadOnly Property ErrorCode As Integer
  Public ReadOnly Property Description As String
End Class

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component throws an exception.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Log Event (CoAP Component)

Fires once for each log message.

Syntax

• C#
• VB.NET

public event OnLogHandler OnLog;

public delegate void OnLogHandler(object sender, CoapLogEventArgs e);

public class CoapLogEventArgs : EventArgs {
  public int LogLevel { get; }
  public string Message { get; }
}

Public Event OnLog As OnLogHandler

Public Delegate Sub OnLogHandler(sender As Object, e As CoapLogEventArgs)

Public Class CoapLogEventArgs Inherits EventArgs
  Public ReadOnly Property LogLevel As Integer
  Public ReadOnly Property Message As String
End Class

Remarks

This event fires once for each log message generated by the component. The verbosity is controlled by the LogLevel setting.

LogLevel indicates the level of the Message. Possible values are:

Notification Event (CoAP Component)

Fires when a notification is received from the server.

Syntax

• C#
• VB.NET

public event OnNotificationHandler OnNotification;

public delegate void OnNotificationHandler(object sender, CoapNotificationEventArgs e);

public class CoapNotificationEventArgs : EventArgs {
  public string URI { get; }
  public bool IsLatest { get; }
  public bool StopObserving { get; set; }
}

Public Event OnNotification As OnNotificationHandler

Public Delegate Sub OnNotificationHandler(sender As Object, e As CoapNotificationEventArgs)

Public Class CoapNotificationEventArgs Inherits EventArgs
  Public ReadOnly Property URI As String
  Public ReadOnly Property IsLatest As Boolean
  Public Property StopObserving As Boolean
End Class

Remarks

This event fires when the component receives a notification from that server that some observed resource has changed. Query the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties to obtain the new resource information.

Note that, in some cases, the server may no longer be able to deliver notifications for a resource (e.g., if it is deleted). In such cases, the ResponseCode property will be populated with a non-2.xx code (e.g., 4.04 "Not Found") to indicate why the resource can no longer be observed. No further notifications will be delivered for the resource after such a notification arrives.

The URI parameter identifies the resource that has changed.

The IsLatest parameter reflects whether this notification actually has the most recent resource information available, since it is possible for notifications to arrive out of order under certain circumstances.

The StopObserving parameter specifies whether the component should stop observing the resource identified by URI. This parameter is False by default, set it to True to have the component unregister itself from further notifications. (Note: in the event of a non-2.xx notification, this parameter will be True by default instead, and changing it to False will have no effect.)

Note: This event is only used when the component is operating in client mode (i.e., when the Listening property is disabled).

Register Event (CoAP Component)

Fires when a client wishes to register for notifications.

Syntax

• C#
• VB.NET

public event OnRegisterHandler OnRegister;

public delegate void OnRegisterHandler(object sender, CoapRegisterEventArgs e);

public class CoapRegisterEventArgs : EventArgs {
  public string RemoteHost { get; }
  public int RemotePort { get; }
  public string URI { get; }
  public string URIHost { get; }
  public int URIPort { get; }
  public string URIPath { get; }
  public string URIQuery { get; }
  public string Token { get; }
  public byte[] TokenB { get; }
  public bool Accept { get; set; }
}

Public Event OnRegister As OnRegisterHandler

Public Delegate Sub OnRegisterHandler(sender As Object, e As CoapRegisterEventArgs)

Public Class CoapRegisterEventArgs Inherits EventArgs
  Public ReadOnly Property RemoteHost As String
  Public ReadOnly Property RemotePort As Integer
  Public ReadOnly Property URI As String
  Public ReadOnly Property URIHost As String
  Public ReadOnly Property URIPort As Integer
  Public ReadOnly Property URIPath As String
  Public ReadOnly Property URIQuery As String
  Public ReadOnly Property Token As String
  Public ReadOnly Property TokenB As Byte()
  Public Property Accept As Boolean
End Class

Remarks

This event fires anytime a client wishes to register itself as an observer for the resource identified by URI. Refer to the StartObserving and SendNotification methods, as well as the Notification event, for more information about observing resources and resource change notifications.

Any options included in the request can be obtained by querying the RequestOptions collection.

To correctly handle this event, populate the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties as desired before this event finishes. (This must be done regardless of the Accept parameter's final value; see below for more information on why).

The RemoteHost parameter reflects the client's IP address or hostname.

The RemotePort parameter reflects the client's port.

The URI parameter reflects the exact resource URI that the client wishes to observe (the CoAP specification states that the full URI must be used to track observers). This value must be passed exactly as-is to the SendNotification method to notify observers of changes to the resource.

The URIHost, URIPort, URIPath, and URIQuery parameters are provided for additional convenience

The Token parameter reflects the token included in the registration request.

The Accept parameter specifies whether the component should accept the registration. By default, it is False, and the request will be treated like a normal GET request. Setting it to True will cause the component to add the client to its internal list of registered observers for the specified URI.

Note: This event is only used when the component is operating in server mode (i.e., when the Listening property is enabled).

Request Event (CoAP Component)

Fires when a request is received from a client.

Syntax

• C#
• VB.NET

public event OnRequestHandler OnRequest;

public delegate void OnRequestHandler(object sender, CoapRequestEventArgs e);

public class CoapRequestEventArgs : EventArgs {
  public string RemoteHost { get; }
  public int RemotePort { get; }
  public int Method { get; }
  public string URIHost { get; }
  public int URIPort { get; }
  public string URIPath { get; }
  public string URIQuery { get; }
  public string Token { get; }
  public byte[] TokenB { get; }
  public string RequestId { get; }
  public bool SendResponse { get; set; }
}

Public Event OnRequest As OnRequestHandler

Public Delegate Sub OnRequestHandler(sender As Object, e As CoapRequestEventArgs)

Public Class CoapRequestEventArgs Inherits EventArgs
  Public ReadOnly Property RemoteHost As String
  Public ReadOnly Property RemotePort As Integer
  Public ReadOnly Property Method As Integer
  Public ReadOnly Property URIHost As String
  Public ReadOnly Property URIPort As Integer
  Public ReadOnly Property URIPath As String
  Public ReadOnly Property URIQuery As String
  Public ReadOnly Property Token As String
  Public ReadOnly Property TokenB As Byte()
  Public ReadOnly Property RequestId As String
  Public Property SendResponse As Boolean
End Class

Remarks

This event fires anytime a request is received from a client. Information about the request is exposed both via this event's parameters and the following properties: RequestData, RequestContentFormat, RequestETag, and RequestOptions.

A response can either be sent back to the client immediately when the event finishes, or later using the SendResponse method. Refer to the RequestId and SendResponse parameters' documentation, below, for more information. If a response is to be sent back immediately, populate the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties as desired before this event finishes.

The RemoteHost parameter reflects the client's IP address or hostname.

The RemotePort parameter reflects the client's port.

The Method parameter reflects the request method code. The following table provides a (non-exhaustive) list of some of the more common method codes; refer to the IANA's CoAP Method Codes registry for a full list.

The URIHost, URIPort, URIPath, and URIQuery parameters, when taken together, identify the resource that the client is making a request against. This event exposes the URI in pieces for convenience.

The Token parameter reflects the token included in the request.

The RequestId parameter reflects the component-generated Id for the request. If the final value of the SendResponse parameter is False, this Id can be passed to the SendResponse method later to send a response. (Alternatively, it can be passed to the CancelRequest later to ignore the request.)

The SendResponse parameter specifies whether the component should send a response back to the client immediately; it is True by default. Set it to False to send the response later instead.

Note: This event is only used when the component is operating in server mode (i.e., when the Listening property is enabled).

RequestComplete Event (CoAP Component)

Fires when a request completes.

Syntax

• C#
• VB.NET

public event OnRequestCompleteHandler OnRequestComplete;

public delegate void OnRequestCompleteHandler(object sender, CoapRequestCompleteEventArgs e);

public class CoapRequestCompleteEventArgs : EventArgs {
  public int Method { get; }
  public string URI { get; }
  public string RequestId { get; }
  public int ErrorCode { get; }
  public string ErrorDescription { get; }
}

Public Event OnRequestComplete As OnRequestCompleteHandler

Public Delegate Sub OnRequestCompleteHandler(sender As Object, e As CoapRequestCompleteEventArgs)

Public Class CoapRequestCompleteEventArgs Inherits EventArgs
  Public ReadOnly Property Method As Integer
  Public ReadOnly Property URI As String
  Public ReadOnly Property RequestId As String
  Public ReadOnly Property ErrorCode As Integer
  Public ReadOnly Property ErrorDescription As String
End Class

Remarks

This event fires when a request completes. Usually, a request is considered complete when a response has been received. However, requests can also be considered "complete" if either of the following occurs:

• If the UseConfirmableMessages property is enabled, and the component did not receive confirmation that the request was received before the retransmission period elapsed.
• If Timeout property is greater than 0, and the component did not receive a response before the timeout period elapsed.

Assuming a response was received (i.e., the ErrorCode parameter is either 0 or 709; see below), then the response code, payload, and options can be obtained by querying the ResponseCode, ResponseData, ResponseContentFormat, ResponseETag, and ResponseOptions properties.

The Method parameter reflects the request method code. The following table provides a (non-exhaustive) list of some of the more common method codes; refer to the IANA's CoAP Method Codes registry for a full list.

The URI parameter reflects the requested resource's URI.

The ErrorCode parameter indicates whether the request encountered an error. If no error was encountered, it will be 0; if the server returned a non-2.xx response code, it will be 709; if some other error occurred (e.g., the request timed out), it will be another non-zero value.

The ErrorDescription parameter provides a description of the error that occurred (or, if ErrorCode is 709, a string version of the response code returned by the server). It will be empty if no error was encountered.

Note: This event is only used when the component is operating in client mode (i.e., when the Listening property is disabled).

ResponseComplete Event (CoAP Component)

Fires when a response has been sent to a client.

Syntax

• C#
• VB.NET

public event OnResponseCompleteHandler OnResponseComplete;

public delegate void OnResponseCompleteHandler(object sender, CoapResponseCompleteEventArgs e);

public class CoapResponseCompleteEventArgs : EventArgs {
  public string RequestId { get; }
  public int ErrorCode { get; }
  public string ErrorDescription { get; }
}

Public Event OnResponseComplete As OnResponseCompleteHandler

Public Delegate Sub OnResponseCompleteHandler(sender As Object, e As CoapResponseCompleteEventArgs)

Public Class CoapResponseCompleteEventArgs Inherits EventArgs
  Public ReadOnly Property RequestId As String
  Public ReadOnly Property ErrorCode As Integer
  Public ReadOnly Property ErrorDescription As String
End Class

Remarks

This event fires anytime a response has been sent to a client. If the UseConfirmableMessages property is enabled, then the response is considered complete once the client has confirmed that it received the response (or once the retransmission period elapses). If the UseConfirmableMessages property is disabled, the response is considered complete immediately (since there is no way to know if the client received it).

The RequestId parameter reflects the component-generated Id of the request for which the response was sent.

The ErrorCode parameter indicates whether the response encountered an error (e.g., transmission timed out). If no error was encountered, it will be 0.

The ErrorDescription parameter provides a description of the error that occurred. It will be empty if no error was encountered.

Note: This event is only used when the component is operating in server mode (i.e., when the Listening property is enabled).

Unregistered Event (CoAP Component)

Fires when a client has unregistered from notifications.

Syntax

• C#
• VB.NET

public event OnUnregisteredHandler OnUnregistered;

public delegate void OnUnregisteredHandler(object sender, CoapUnregisteredEventArgs e);

public class CoapUnregisteredEventArgs : EventArgs {
  public string RemoteHost { get; }
  public int RemotePort { get; }
  public string URI { get; }
  public string URIHost { get; }
  public int URIPort { get; }
  public string URIPath { get; }
  public string URIQuery { get; }
}

Public Event OnUnregistered As OnUnregisteredHandler

Public Delegate Sub OnUnregisteredHandler(sender As Object, e As CoapUnregisteredEventArgs)

Public Class CoapUnregisteredEventArgs Inherits EventArgs
  Public ReadOnly Property RemoteHost As String
  Public ReadOnly Property RemotePort As Integer
  Public ReadOnly Property URI As String
  Public ReadOnly Property URIHost As String
  Public ReadOnly Property URIPort As Integer
  Public ReadOnly Property URIPath As String
  Public ReadOnly Property URIQuery As String
End Class

Remarks

This event fires anytime a client has unregistered itself from further notifications for the resource identified by URI. Refer to the StartObserving and SendNotification methods, as well as the Notification and Register events, for more information about observing resources and resource change notifications.

The RemoteHost parameter reflects the client's IP address or hostname.

The RemotePort parameter reflects the client's port.

The URI parameter identifies the resource that the client has stopped observing.

The URIHost, URIPort, URIPath, and URIQuery parameters are provided for additional convenience

Note: This event is only used when the component is operating in server mode (i.e., when the Listening property is enabled).

CoAPOption Type

A CoAP option.

Remarks

This type represents a CoAP option.

Fields

Constructors

• C#
• VB.NET

public CoAPOption();

Public CoAPOption()

• C#
• VB.NET

public CoAPOption(int number, string value);

Public CoAPOption(ByVal Number As Integer, ByVal Value As String)

CoAPRequest Type

A pending CoAP request.

Remarks

This type represents a pending CoAP request.

Fields

Config Settings (CoAP Component)

UDP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (CoAP Component)

CoAP Errors