DTLSClient Class

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The DTLSClient class provides client-side functionality for secure UDP communication utilizing the Datagram Transport Layer Security (DTLS) protocol.

Syntax

ipworksdtls.dtlsclient()

Remarks

The DTLSClient class functions as a client that facilitates in connecting to DTLS servers and offers a convenient means of transmitting and receiving datagrams over the established, secure connection.

Connecting to a Server

First, the RemoteHost and RemotePort must be set to the address and port of the target DTLS server. The Timeout property can be used to specify a timeout when connecting to the server. To initiate the connection, call Connect.

After doing so, the handshake process will begin. Relevant handshake details will be reported by the SSLStatus event. Initially, the server will present its certificate to the client. The certificate can be evaluated within the SSLServerAuthentication event. By default, the class will provide a recommendation of whether to accept or reject the certificate, and reasoning behind the recommendation. Regardless, the certificate can be manually accepted (or rejected) within this event.

In some cases, the server requires the client to present a certificate as well. In this case, a valid certificate will need to be specified via the SSLCert property.

Once the connection is complete (or fails), the Connected event will fire. Note that this event will fire if a connection succeeds or fails. If successful, the event will fire with a StatusCode of 0. If this value is non-zero, it indicates the connection was unsuccessful. The Description parameter will contain relevant details. Upon successful connection, the Connected property will be set to True. This process may look like the following:

dtlsclient.OnConnected += (o, e) => { if (e.StatusCode == 0) { Console.WriteLine("Connection successful!"); } else { Console.WriteLine("Connection failed."); Console.WriteLine("Error code: " + e.StatusCode); Console.WriteLine("Error description: " + e.Description); } }; dtlsclient.OnSSLServerAuthentication += (o, e) => { if (e.Accept) return; Console.Write("Server provided the following certificate:\nIssuer: " + e.CertIssuer + "\nSubject: " + e.CertSubject + "\n"); Console.Write("The following problems have been determined for this certificate: " + e.Status + "\n"); Console.Write("Would you like to accept anyways? [y/n] "); if (Console.Read() == 'y') e.Accept = true; }; dtlsclient.RemoteHost = "remote_ip"; dtlsclient.RemotePort = 1234; dtlsclient.Timeout = 30; // if client authentication is applicable dtlsclient.SSLCert = new Certificate("/path/to/cert.pfx", CertStoreTypes.cstPFXFile, "cert_password", "cert_subject"); dtlsclient.Connect();

Sending and Receiving Data

Once a successful connection is established, the class can send data to the server via SendText or SendBytes.

The class will also be able to receive data from the server via the DataIn event. Note that this event is non-reentrant, and it is recommended to offload time-consuming operations to ensure the best performance.

If required, the PauseData method can be called, disabling the reception of incoming data from the server. Data reception can later be enabled via the ProcessData method. Note that if this reception is disabled, the server may continue sending data, which will remain unprocessed by the class. In this case, the underlying socket buffer may be filled. This can result in possible data loss originating from the server. Please use these methods with caution.

The complete process may look like the following:

dtlsclient.OnSSLServerAuthentication += (o, e) => { e.Accept = true; }; dtlsclient.OnDataIn += (o, e) => { Console.WriteLine("Packet received from server."); Console.WriteLine("Datagram: " + e.Datagram); } dtlsclient.RemoteHost = "remote_ip"; dtlsclient.RemotePort = 1234; dtlsclient.Connect(); dtlsclient.SendText("Hello World!"); while (true) { dtlsclient.DoEvents(); }

Disconnecting from a Server

Once the connection to the server is broken, the Disconnected event will fire. The disconnection can be performed by calling Disconnect, or performed by the server.

In the case a connection ends and an error is encountered, the StatusCode and Description parameters will contain relevant details regarding the error. For example:

dtlsclient.OnDisconnected += (o, e) => { if (e.StatusCode == 0) { Console.WriteLine("Connection ended."); } else { Console.WriteLine("Connection ended."); Console.WriteLine("Error code: " + e.StatusCode); Console.WriteLine("Error description: " + e.Description); } }; dtlsclient.RemoteHost = "remote_ip"; dtlsclient.RemotePort = 1234; dtlsclient.Connect(); ... ... ... dtlsclient.Disconnect();

Additional Information

To support KeepAlive functionality, it is important to note that DoEvents must be called regularly in both console and form-based applications. This is to ensure the class sends keep-alive (or Heartbeat) packets to the server in a timely manner.

In form-based applications, this does not apply if KeepAlive is False.

Property List

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

Method List

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

Event List

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

Config Settings

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

DTLSClient.AcceptData Property

This property indicates whether data reception is currently enabled.

Syntax

isAcceptData(): boolean;

Default Value

TRUE

Remarks

This property indicates whether data reception is currently enabled. When false, data reception is disabled and the DataIn event will not fire. Use the PauseData and ProcessData methods to pause and resume data reception.

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

DTLSClient.Connected Property

This property indicates whether the class is connected.

Syntax

isConnected(): boolean;

Default Value

FALSE

Remarks

This property indicates whether the class is connected to the remote host. Use the Connect and Disconnect methods to manage the connection.

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

DTLSClient.KeepAlive Property

When True, keep-alive functionality is enabled via the DTLS Heartbeat Extension.

Syntax

isKeepAlive(): boolean;
setKeepAlive(keepAlive: boolean): void;

Default Value

FALSE

Remarks

This property enables keep-alive functionality for the established connection via the DTLS Heartbeat Extension (RFC 6520). Enabling this option can prevent a long connection from timing out in case of inactivity.

Note: For this functionality to work as intended, DoEvents must be called frequently in both console and form-based applications (e.g., using a loop or timer).

Additionally, DTLS server implementations are not required to support Heartbeats.

DTLSClient.LocalHost Property

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

Syntax

getLocalHost(): string;
setLocalHost(localHost: string): void;

Default Value

""

Remarks

This 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 multihomed hosts (machines with more than one IP interface) setting LocalHost to the IP address of an interface will make the class initiate connections (or accept in the case of server classs) only through that interface. It is recommended to provide an IP address rather than a hostname when setting this property to ensure the desired interface is used.

If the class 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 multihomed 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.

DTLSClient.LocalPort Property

This property includes the User Datagram Protocol (UDP) port in the local host where UDP binds.

Syntax

getLocalPort(): number;
setLocalPort(localPort: number): void;

Default Value

0

Remarks

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

Setting it to 0 (default) enables the Transmission Control Protocol (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 class is Active. Any attempt to set the LocalPort property when the class is Active will generate an error.

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

DTLSClient.RemoteHost Property

This property includes the address of the remote host. Domain names are resolved to IP addresses.

Syntax

getRemoteHost(): string;
setRemoteHost(remoteHost: string): void;

Default Value

""

Remarks

The RemoteHost property specifies the IP address (IP number in dotted internet format) or domain name of the remote host.

If RemoteHost is set to 255.255.255.255, the class broadcasts data on the local subnet.

If the RemoteHost property is set to a domain name, a DNS request is initiated, and upon successful termination of the request, the RemoteHost property is set to the corresponding address. If the search is not successful, an error is returned.

If UseConnection is set to True, the RemoteHost must be set before the class is activated (Active is set to True).

DTLSClient.RemotePort Property

This property specifies the User Datagram Protocol (UDP) port in the remote host.

Syntax

getRemotePort(): number;
setRemotePort(remotePort: number): void;

Default Value

0

Remarks

The RemotePort is the UDP port on the RemoteHost to send UDP datagrams to.

A valid port number (a value between 1 and 65535) is required.

If UseConnection is set to True, the RemotePort must be set before the class is activated (Active is set to True).

DTLSClient.SSLAcceptServerCert Property

Instructs the class to unconditionally accept the server certificate that matches the supplied certificate.

Syntax

getSSLAcceptServerCert(): Certificate;
setSSLAcceptServerCert(SSLAcceptServerCert: Certificate): void;

Default Value

Remarks

If it finds any issues with the certificate presented by the server, the class will normally terminate the connection with an error.

You may override this behavior by supplying a value for SSLAcceptServerCert. If the certificate supplied in SSLAcceptServerCert is the same as the certificate presented by the server, then the server certificate is accepted unconditionally, and the connection will continue normally.

Note: This functionality is provided only for cases in which you otherwise know that you are communicating with the right server. If used improperly, this property may create a security breach. Use it at your own risk.

DTLSClient.SSLCert Property

The certificate to be used during Secure Sockets Layer (SSL) negotiation.

Syntax

getSSLCert(): Certificate;
setSSLCert(SSLCert: Certificate): void;

Default Value

Remarks

This property includes the digital certificate that the class will use during SSL negotiation. Set this property to a valid certificate before starting SSL negotiation. To set a certificate, you may set the field to the encoded certificate. To select a certificate, use the store and subject fields.

DTLSClient.SSLServerCert Property

The server certificate for the last established connection.

Syntax

getSSLServerCert(): Certificate;

Default Value

Remarks

This property contains the server certificate for the last established connection.

SSLServerCert is reset every time a new connection is attempted.

This property is read-only.

DTLSClient.Timeout Property

This property specifies a timeout when connecting to a server.

Syntax

getTimeout(): number;
setTimeout(timeout: number): void;

Default Value

60

Remarks

This property specifies a timeout when connecting to a server. When calling Connect, if the connection is not established within Timeout seconds, an error is thrown.

DTLSClient.config Method

Sets or retrieves a configuration setting.

Syntax

async dtlsclient.config(configurationString : string): Promise<string>

Remarks

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

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, 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.

DTLSClient.connect Method

This method connects to a remote host.

Syntax

async dtlsclient.connect(): Promise<void>

Remarks

This method connects to the remote host specified by RemoteHost and RemotePort. For instance: component.RemoteHost = "MyHostNameOrIP"; component.RemotePort = 7777; component.Connect();

DTLSClient.disconnect Method

This method disconnects from the remote host.

Syntax

async dtlsclient.disconnect(): Promise<void>

Remarks

This method disconnects from the remote host. Calling this method is equivalent to setting the Connected property to False.

DTLSClient.doEvents Method

This method processes events from the internal message queue.

Syntax

async dtlsclient.doEvents(): Promise<void>

Remarks

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

DTLSClient.pauseData Method

This method pauses data reception.

Syntax

async dtlsclient.pauseData(): Promise<void>

Remarks

This method pauses data reception when called. While data reception is paused, the DataIn event will not fire. Call ProcessData to reenable data reception.

DTLSClient.processData Method

This method reenables data reception after a call to PauseData .

Syntax

async dtlsclient.processData(): Promise<void>

Remarks

This method reenables data reception after a previous call to PauseData. When PauseData is called, the DataIn event will not fire. To reenable data reception and allow DataIn to fire, call this method.

Note: This method is used only after previously calling PauseData. It does not need to be called to process incoming data by default.

DTLSClient.reset Method

This method will reset the class.

Syntax

async dtlsclient.reset(): Promise<void>

Remarks

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

DTLSClient.sendBytes Method

This method sends binary data to the remote host.

Syntax

async dtlsclient.sendBytes(data : Uint8Array): Promise<void>

Remarks

This method sends the specified binary data to the remote host. For example:

byte[] dataToSend = new byte[] { 72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33 }; dtlsclient.SendBytes(dataToSend);

To send text, use the SendText method instead.

DTLSClient.sendText Method

This method sends text to the remote host.

Syntax

async dtlsclient.sendText(text : string): Promise<void>

Remarks

This method sends the specified text to the remote host. For example:

dtlsclient.onSSLServerAuthentication += (o, e) => { e.Accept = true; }; dtlsclient.RemotePort = 8765; dtlsclient.RemoteHost = "HostNameOrIPAddress"; dtlsclient.Connect(); dtlsclient.SendText("Hello!");

To send binary data, use the SendBytes method instead.

DTLSClient.Connected Event

This event is fired immediately after a connection completes (or fails).

Syntax

dtlsclient.on('Connected', listener: (e: {readonly address: string, readonly port: number, readonly statusCode: number, readonly description: string}) => void )

Remarks

This event is fired immediately after a connection completes (or fails).

If the connection is made normally, StatusCode is 0 and Description is "OK".

If the connection is broken for any other reason, StatusCode will be non-zero, and the Description parameter will contain a description of this code.

DTLSClient.DataIn Event

This event is fired when data are received.

Syntax

dtlsclient.on('DataIn', listener: (e: {readonly datagram: string, readonly datagramB: Uint8Array, readonly sourceAddress: string, readonly sourcePort: number}) => void )

Remarks

The DataIn event is fired every time a new datagram is received.

Datagram contains the packet as sent by the remote host.

SourceAddress contains the IP number (Internet address) of the remote host, and SourcePort contains the port from which the packet originated.

Note: Events are not re-entrant. Performing time-consuming operations within this event will prevent it from firing again in a timely manner and may affect overall performance.

DTLSClient.Disconnected Event

This event is fired when a connection is closed.

Syntax

dtlsclient.on('Disconnected', listener: (e: {readonly address: string, readonly port: number, readonly statusCode: number, readonly description: string}) => void )

Remarks

This event is fired when a connection is closed.

If the connection is broken normally, StatusCode is 0 and Description is "OK".

If the connection is broken for any other reason, StatusCode will be non-zero, and the Description parameter will contain a description of this code.

DTLSClient.Error Event

Fired when information is available about errors during data delivery.

Syntax

dtlsclient.on('Error', listener: (e: {readonly errorCode: number, readonly description: string}) => void )

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the class .

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.

DTLSClient.Log Event

This event fires once for each log message.

Syntax

dtlsclient.on('Log', listener: (e: {readonly logLevel: number, readonly message: string, readonly logType: string}) => void )

Remarks

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

LogLevel indicates the level of message. Possible values are as follows:

The value 1 (Info) logs basic information, including users logging in and out, files transferred, and directories listed.

The value 2 (Verbose) includes logs from the PITrail event as well as basic information about data transfer channels.

The value 3 (Debug) logs additional debug information, such as extended socket connection and data transfer information.

Message is the log entry.

LogType identifies the type of log entry. Possible values are as follows:

• "Info"
• "Error"
• "Verbose"
• "Debug"

DTLSClient.SSLServerAuthentication Event

This event is fired after the server presents its certificate to the client.

Syntax

dtlsclient.on('SSLServerAuthentication', listener: (e: {readonly sourceAddress: string, readonly sourcePort: number, readonly certEncoded: string, readonly certEncodedB: Uint8Array, readonly certSubject: string, readonly certIssuer: string, readonly status: string, accept: boolean}) => void )

Remarks

This event is fired after the server presents its certificate to the client.

During this event, the client can decide whether or not to continue with the connection process. The Accept parameter is a recommendation on whether to continue or close the connection. This is just a suggestion: application software must use its own logic to determine whether or not to continue.

When Accept is False, Status shows why the verification failed (otherwise, Status contains the string OK). If it is decided to continue, you can override and accept the certificate by setting the Accept parameter to True.

DTLSClient.SSLStatus Event

Fired when secure connection progress messages are available.

Syntax

dtlsclient.on('SSLStatus', listener: (e: {readonly message: string}) => void )

Remarks

The event is fired for informational and logging purposes only. This event tracks the progress of the connection.

Certificate Type

This is the digital certificate being used.

Remarks

This type describes the current digital certificate. The certificate may be a public or private key. The fields are used to identify or select certificates.

Fields

Constructors

public Certificate();

public Certificate(String certificateFile);

public Certificate(byte[] encoded);

public Certificate(int storeType, String store, String storePassword, String subject);

public Certificate(int storeType, String store, String storePassword, String subject, String configurationString);

public Certificate(int storeType, String store, String storePassword, byte[] encoded);

public Certificate(int storeType, byte[] store, String storePassword, String subject);

public Certificate(int storeType, byte[] store, String storePassword, String subject, String configurationString);

public Certificate(int storeType, byte[] store, String storePassword, byte[] encoded);

Config Settings (class ipworksdtls.dtlsclient)

DTLSClient Config Settings

UDP Config Settings

Socket Config Settings

SSL Config Settings

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
... Intermediate Cert ...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
... Root Cert ...
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
... Intermediate Cert ...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
... Root Cert ...
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
... Intermediate Cert...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
... Root Cert...
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

Base Config Settings

Trappable Errors (class ipworksdtls.dtlsclient)

DTLSClient Errors