BLEServer Module

Properties   Methods   Events   Config Settings   Errors  

An easy-to-use Bluetooth Low Energy (BLE) GATT Server module.

Syntax

IPWorksBLE.BLEServer

Remarks

The BLEServer module provides a simple but flexible BLE GATT server (peripheral) implementation, making it easy to advertise your own services and characteristics, and to respond to the requests of remote BLE GATT clients that connect to them.

Prerequisites

Windows Notes:

Please note that the BLE modules are only supported by Windows 10 Creator's Update (10.0.15063.0) and later.

Android Notes:

The BLE modules require an Android API level of 21 or higher.

Note that on Android, even when pairing is not explicitly enabled in the component, the operating system may automatically perform pairing as it deems appropriate.

iOS/macOS Notes:

The BLE modules have the following operating system requirements:

• iOS 5.0+
• iPadOS 5.0+
• Mac Catalyst 13.0+
• macOS 10.10+

Linux Notes:

On Linux, the BLE modules rely on BlueZ and DBus. These packages must be installed in order to use the components. Many Linux distributions come with BlueZ and DBus pre-installed.

Adding Services and Characteristics

As with BLEClient, UUIDs may be given as 16-, 32-, or 128-bit hexadecimal strings (a mixture of formats is fine; they're all converted to 128-bit internally).

Props is a bitmask made up of one or more of the following flags:

• 0x0002 (Read): The characteristic's value may be read by clients. Handle the ReadRequested event to supply the value.
• 0x0004 (WriteWithoutResponse): Clients may write the characteristic's value without expecting an acknowledgement.
• 0x0008 (Write): Clients may write the characteristic's value and receive an acknowledgement indicating success or failure.
• 0x0010 (Notify): Clients may subscribe to receive unacknowledged notifications when the characteristic's value changes.
• 0x0020 (Indicate): Clients may subscribe to receive acknowledged indications when the characteristic's value changes.

// Add a simple read-only "Battery Level" characteristic to a "Battery Service". bleserver1.AddCharacteristic("180F", "2A19", 0x0002);

Refer to AddCharacteristic for more detailed information.

Advertising

You can check whether a particular service is currently being advertised by setting the ServiceId property to its UUID, and then inspecting the Listening property. Call StopListening to stop advertising a service.

// AdvertisementStatusChanged event handler. bleserver1.OnAdvertisementStatusChanged += (s, e) => Console.WriteLine("Advertising status: " + e.Status); bleserver1.StartListening("180F"); // ... bleserver1.StopListening("180F");

Handling Client Requests

Handle the ReadRequested event to respond to read requests for characteristics that have the Read flag set. Set the event's ResponseValue parameter to a hex-encoded string holding the bytes to return, and leave its Accept parameter set to its default value of True. To reject the request instead, set Accept to False.

bleserver1.OnReadRequested += (s, e) => { if (e.CharacteristicId.Equals("00002A19-0000-1000-8000-00805F9B34FB", StringComparison.OrdinalIgnoreCase)) { e.ResponseValue = "5A"; // 90 (%), as a single hex-encoded byte. } else { e.Accept = false; } };

Similarly, handle the WriteRequested event to respond to write requests for characteristics that have the Write or WriteWithoutResponse flag set. Its Value parameter holds the hex-encoded string of bytes the client wants to write, and WithResponse indicates whether the client is expecting an acknowledgement. Set Accept to False to reject a write made with acknowledgement; Accept has no effect on writes made without acknowledgement, since the client isn't told the outcome either way.

bleserver1.OnWriteRequested += (s, e) => { Console.WriteLine("Client wrote: " + e.Value); };

Handle the SubscriptionChanged event to know when a Notify or Indicate characteristic gains or loses subscribed clients, and the SessionStatusChanged and Disconnected events to track a client's connection over time.

Once a client has subscribed to a Notify or Indicate characteristic, call UpdateValue whenever its value changes to push the new value to every currently subscribed client. If no clients are currently subscribed, calling UpdateValue has no effect.

// Push a new value to all clients subscribed to notifications/indications on this characteristic. bleserver1.UpdateValue("180F", "2A19", new byte[] { 0x5A });

Usage Notes

Most platforms will in some way limit the use of Bluetooth APIs when your application is in the background. Be aware of the limitations your platform places on the usage of BLE APIs while in the background, and be ready to act accordingly.

Be sure to call StopListening for each of your services when you're finished advertising them.

Property List

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

Method List

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

Event List

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

Config Settings

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

Characteristics Property (BLEServer Module)

The GATT characteristics which have been added to the server.

Syntax

• Swift
• Objective-C

public var characteristics: Array<ServerCharacteristic> {
  get {...}
}

@property (nonatomic,readonly,assign,getter=characteristicCount) int characteristicCount;

- (int)characteristicCount;

- (BOOL)characteristicCanSubscribe:(int)characteristicIndex;

- (int)characteristicFlags:(int)characteristicIndex;

- (NSString*)characteristicId:(int)characteristicIndex;

- (NSString*)characteristicServiceId:(int)characteristicIndex;

- (NSString*)characteristicUuid:(int)characteristicIndex;

Remarks

The GATT characteristics which have been added to the server through calls to the AddCharacteristic method. This collection is read-only.

This property is read-only.

Listening Property (BLEServer Module)

Whether the service identified by ServiceId is currently being advertised.

Syntax

• Swift
• Objective-C

public var listening: Bool {
  get {...}
}

@property (nonatomic,readonly,assign,getter=listening) BOOL listening;

- (BOOL)listening;

Default Value

False

Remarks

This property indicates whether the service identified by the ServiceId property is currently being advertised, and can therefore be discovered by remote clients.

Use the StartListening and StopListening methods to start and stop advertising a service.

This property is read-only.

If an error occurs when setting this property an error will not be thrown. This property has a related method which will throw an error:

public func setListening(listening: Bool) throws

ServiceId Property (BLEServer Module)

The Id of the service to check the listening status of.

Syntax

• Swift
• Objective-C

public var serviceId: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=serviceId,setter=setServiceId:) NSString* serviceId;

- (NSString*)serviceId;
- (void)setServiceId :(NSString*)newServiceId;

Default Value

""

Remarks

Set ServiceId to the Id of a service you've added characteristics to (via AddCharacteristic) in order to inspect its advertising status using the Listening property.

Services are identified by the same UUID string passed to AddCharacteristic, StartListening, and StopListening.

Services Property (BLEServer Module)

The GATT services which have been added to the server.

Syntax

• Swift
• Objective-C

public var services: Array<ServerService> {
  get {...}
}

@property (nonatomic,readonly,assign,getter=serviceCount) int serviceCount;

- (int)serviceCount;

- (NSString*)serviceInstanceId:(int)serviceIndex;

- (NSString*)serviceUuid:(int)serviceIndex;

Remarks

The GATT services which have been added to the server through calls to the AddCharacteristic method. This collection is read-only.

This property is read-only.

AddCharacteristic Method (BLEServer Module)

Adds a characteristic to a service, creating the service if necessary.

Syntax

• Swift
• Objective-C

public func addCharacteristic(serviceId: String, characteristicId: String, props: Int32) throws -> Void

- (void)addCharacteristic :(NSString*)serviceId :(NSString*)characteristicId :(int)props;

Remarks

This method adds a characteristic, identified by CharacteristicId, to the service identified by ServiceId. If no service with that Id has been added yet, it is created automatically.

ServiceId and CharacteristicId are UUID strings, and may be specified using 16-, 32-, or 128-bit hexadecimal notation (dashes are optional); they are converted to full 128-bit UUIDs internally.

Props is a bitmask describing the operations remote clients are permitted to perform on the characteristic once it starts being advertised. It should be one or more of the following flags, combined with a bitwise OR:

A characteristic cannot be added to a service that is already being advertised (see StartListening); doing so will cause the module to . Once a service has started listening, its set of characteristics is fixed until you call StopListening.

// Add a read-only "Battery Level" characteristic to a "Battery Service". bleserver1.AddCharacteristic("180F", "2A19", 0x0002); // Add a write-only "Alert Level" characteristic to an "Immediate Alert" service. bleserver1.AddCharacteristic("1802", "2A06", 0x0008);

Config Method (BLEServer Module)

Sets or retrieves a configuration setting.

Syntax

• Swift
• Objective-C

public func config(configurationString: String) throws -> String

- (NSString*)config :(NSString*)configurationString;

Remarks

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

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

DoEvents Method (BLEServer Module)

This method processes events from the internal message queue.

Syntax

• Swift
• Objective-C

public func doEvents() throws -> Void

- (void)doEvents;

Remarks

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

StartListening Method (BLEServer Module)

Begins advertising a service so that remote clients can discover and connect to it.

Syntax

• Swift
• Objective-C

public func startListening(serviceId: String) throws -> Void

- (void)startListening :(NSString*)serviceId;

Remarks

This method begins advertising the service identified by ServiceId, making it discoverable by nearby GATT clients. ServiceId must identify a service that characteristics have already been added to via AddCharacteristic.

The AdvertisementStatusChanged event fires once advertising actually starts (and again if it later stops or is aborted). You can check whether a service is currently being advertised at any time by setting the ServiceId property to its Id and inspecting the Listening property.

Calling this method for a service that doesn't exist, or that is already being advertised, will cause the module to .

bleserver1.AddCharacteristic("180F", "2A19", 0x0002); bleserver1.StartListening("180F");

StopListening Method (BLEServer Module)

Stops advertising a service.

Syntax

• Swift
• Objective-C

public func stopListening(serviceId: String) throws -> Void

- (void)stopListening :(NSString*)serviceId;

Remarks

This method stops advertising the service identified by ServiceId.

The AdvertisementStatusChanged event fires once advertising has actually stopped.

Calling this method for a service that doesn't exist, or that isn't currently being advertised, will cause the module to .

bleserver1.StopListening("180F");

UpdateValue Method (BLEServer Module)

Updates the value of a characteristic and sends a notification or indication to all currently subscribed clients.

Syntax

• Swift
• Objective-C

public func updateValue(serviceId: String, characteristicId: String, value: Data) throws -> Void

- (void)updateValue :(NSString*)serviceId :(NSString*)characteristicId :(NSData*)value;

Remarks

This method broadcasts a value to all subscribed clients. It does not target a specific client.

The value is specified as a byte array. The characteristic must support notifications or indications. If no clients are subscribed, no notification is sent.

Calling this method for a service that is not currently being advertised will cause the module to .

AdvertisementStatusChanged Event (BLEServer Module)

Fired when the advertising status of a service changes.

Syntax

• Swift
• Objective-C

func onAdvertisementStatusChanged(status: Int32, error: Int32)

- (void)onAdvertisementStatusChanged :(int)status :(int)error;

Remarks

This event fires in response to StartListening and StopListening, and also if advertising is unexpectedly aborted by the underlying Bluetooth stack (for example, because the adapter was disabled).

Status indicates whether advertising has started, stopped, or was aborted; Error holds the underlying Bluetooth-stack error code if Status indicates an abort, or 0 otherwise. The exact numeric values used for Status are platform-dependent.

Note that this event does not identify which service's advertising status has changed. If you are advertising more than one service at a time, set the ServiceId property to each of your service Ids in turn and check the Listening property to determine which one this event pertains to.

Connected Event (BLEServer Module)

Fired when a remote client connects.

Syntax

• Swift
• Objective-C

func onConnected(clientId: String, statusCode: Int32, description: String)

- (void)onConnected :(NSString*)clientId :(int)statusCode :(NSString*)description;

Remarks

The underlying Bluetooth APIs do not notify the module when a remote device forms a low-level BLE connection to it. Instead, this event fires the first time a client interacts with one of your characteristics, by reading it (ReadRequested), writing it (WriteRequested), or subscribing to it (SubscriptionChanged).

ClientId is a platform-specific string that identifies the client, and is also provided as a parameter to the events above, as well as SessionStatusChanged and Disconnected, so that you can associate requests with a particular client.

StatusCode is always 0 and Description is always "OK", since a connection has, by definition, already been established by the time this event can fire.

Disconnected Event (BLEServer Module)

Fired when a connected client disconnects.

Syntax

• Swift
• Objective-C

func onDisconnected(clientId: String, statusCode: Int32, description: String)

- (void)onDisconnected :(NSString*)clientId :(int)statusCode :(NSString*)description;

Remarks

This event fires when the GATT session for a previously-connected client (see Connected) is closed; refer to SessionStatusChanged for more information about session state changes.

ClientId identifies which client disconnected. StatusCode is always 0 and Description is always "OK".

If the disconnecting client had any active characteristic subscriptions, the SubscriptionChanged event will fire separately to reflect their removal.

Error Event (BLEServer Module)

Fired when information is available about errors during data delivery.

Syntax

• Swift
• Objective-C

func onError(errorCode: Int32, description: String)

- (void)onError :(int)errorCode :(NSString*)description;

Remarks

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

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 (BLEServer Module)

Fires once for each log message.

Syntax

• Swift
• Objective-C

func onLog(logLevel: Int32, message: String, logType: String)

- (void)onLog :(int)logLevel :(NSString*)message :(NSString*)logType;

Remarks

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

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

The default log level, Info, provides information when most BLE operations begin and end, and should be sufficient to get a good idea of what the module is doing at a high level.

The Verbose log level adds a few extra operation timing messages, and adds more detail to some messages logged at the Info level.

The Debug log level causes the module to output as much information as possible about what it is doing at all times. All BLE communications, even those which are typically abstracted away by the API, are logged in full detail. Typically the additional information added by this log level is not helpful to the end user, and would only be necessary to capture if you wish to report an issue to the support team.

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

• Connection: Messages relating to connecting, disconnecting, and connection failures.
• Read: Messages relating to reading values from the remote device.
• Write: Messages relating to writing values to the remote device.
• Subscriptions: Messages relating to subscribing to and unsubscribing from characteristics.
• Info, Verbose, and Debug: Miscellaneous messages fired at the applicable log level concerning internal module operations.

ReadRequested Event (BLEServer Module)

Fired when a client requests to read a characteristic's value.

Syntax

• Swift
• Objective-C

func onReadRequested(clientId: String, serviceId: String, characteristicId: String, responseValue: inout String, accept: inout Bool)

- (void)onReadRequested :(NSString*)clientId :(NSString*)serviceId :(NSString*)characteristicId :(NSString**)responseValue :(int*)accept;

Remarks

This event fires when a connected client sends a request to read the current value of a characteristic that was added (via AddCharacteristic) with the Read flag set.

ClientId identifies the requesting client, and ServiceId and CharacteristicId identify the characteristic being read.

To answer the request, set ResponseValue to a hex-encoded string representing the bytes to return to the client, and leave Accept set to its default value of True. If you do not set ResponseValue, an empty value is returned. To reject the request instead (for example, if the value isn't currently available), set Accept to False.

bleserver1.OnReadRequested += (s, e) => { if (e.CharacteristicId.Equals("00002A19-0000-1000-8000-00805F9B34FB", StringComparison.OrdinalIgnoreCase)) { // Battery Level characteristic: respond with 90%, encoded as a single hex byte. e.ResponseValue = "5A"; } else { e.Accept = false; } };

SessionStatusChanged Event (BLEServer Module)

Fired when a connected client's GATT session status changes.

Syntax

• Swift
• Objective-C

func onSessionStatusChanged(clientId: String, status: Int32, error: Int32)

- (void)onSessionStatusChanged :(NSString*)clientId :(int)status :(int)error;

Remarks

This event fires whenever the underlying GATT session for a connected client (see Connected) becomes active or is closed. It may fire more than once for the same client over the lifetime of a connection, for instance if the client temporarily goes out of range.

ClientId identifies the client. Status indicates whether the session is now active or closed (the exact numeric values used are platform-dependent). Error holds the underlying Bluetooth-stack error code associated with the change, or 0 if there isn't one.

When Status indicates that a client's session has closed, the Disconnected event fires immediately afterward for the same client.

SubscriptionChanged Event (BLEServer Module)

Fired when a characteristic gains or loses a subscribed client.

Syntax

• Swift
• Objective-C

func onSubscriptionChanged(serviceId: String, characteristicId: String, isSubscribed: Bool)

- (void)onSubscriptionChanged :(NSString*)serviceId :(NSString*)characteristicId :(BOOL)isSubscribed;

Remarks

This event fires when a client subscribes to, or unsubscribes from, notifications or indications on a characteristic that was added (via AddCharacteristic) with the Notify or Indicate flag set.

ServiceId and CharacteristicId identify the characteristic. IsSubscribed reflects the characteristic's overall subscription state: True if it now has one or more subscribed clients, or False if it has none. This event does not indicate which specific client subscribed or unsubscribed, nor how many clients are currently subscribed.

To push a new value to any subscribed clients, use UpdateValue.

WriteRequested Event (BLEServer Module)

Fired when a client requests to write a characteristic's value.

Syntax

• Swift
• Objective-C

func onWriteRequested(clientId: String, serviceId: String, characteristicId: String, value: Data, withResponse: Bool, accept: inout Bool)

- (void)onWriteRequested :(NSString*)clientId :(NSString*)serviceId :(NSString*)characteristicId :(NSData*)value :(BOOL)withResponse :(int*)accept;

Remarks

This event fires when a connected client sends a request to write a new value to a characteristic that was added (via AddCharacteristic) with the Write or WriteWithoutResponse flag set.

ClientId identifies the requesting client, and ServiceId and CharacteristicId identify the characteristic being written to. Value holds the hex-encoded string of bytes the client wants to write. WithResponse is True if the client is expecting an acknowledgement (a "Write"), or False if it is not (a "Write Without Response").

If WithResponse is True, the response will use Accept to indicate if the request was accepted or rejected.

bleserver1.OnWriteRequested += (s, e) => { Console.WriteLine("Client " + e.ClientId + " wrote: " + e.Value); };

ServerCharacteristic Type

A GATT characteristic added to a BLE server.

Remarks

This type represents a GATT characteristic added to a BLE server.

• CanSubscribe
• Flags
• Id
• ServiceId
• Uuid

Fields

Constructors

public init()

ServerService Type

A GATT service added to a BLE server.

Remarks

This type represents a GATT service added to a BLE server.

• InstanceId
• Uuid

Fields

Constructors

public init()

Config Settings (BLEServer Module)

BLEServer Config Settings

Base Config Settings

Trappable Errors (BLEServer Module)

BLEServer Errors