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Use the SignalR output binding to send one or more messages using Azure SignalR Service. You can broadcast a message to:
The output binding also allows you to manage groups, such as adding a client or user to a group, removing a client or user from a group.
For information on setup and configuration details, see the overview.
A C# function can be created by using one of the following C# modes:
Important
Support will end for the in-process model on November 10, 2026. We highly recommend that you migrate your apps to the isolated worker model for full support.
The following example shows a function that sends a message using the output binding to all connected clients. The target is the name of the method to be invoked on each client. The Arguments property is an array of zero or more objects to be passed to the client method.
[FunctionName("SendMessage")]
public static Task SendMessage(
[HttpTrigger(AuthorizationLevel.Anonymous, "post")]object message,
[SignalR(HubName = "hubName1")]IAsyncCollector<SignalRMessage> signalROutput)
{
return signalROutput.AddAsync(
new SignalRMessage
{
Target = "newMessage",
Arguments = new [] { message }
});
}
Here's binding data in the function.json file:
Example function.json:
{
"type": "signalR",
"name": "signalROutput",
"hubName": "hubName1",
"connectionStringSetting": "<name of setting containing SignalR Service connection string>",
"direction": "out"
}
const { app, output } = require('@azure/functions');
const signalR = output.generic({
type: 'signalR',
name: 'signalR',
hubName: 'hub',
connectionStringSetting: 'AzureSignalRConnectionString',
});
// You can use any other trigger type instead.
app.http('broadcast', {
methods: ['GET'],
authLevel: 'anonymous',
extraOutputs: [signalR],
handler: (request, context) => {
context.extraOutputs.set(signalR, {
"target": "newMessage",
"arguments": [request.body]
});
}
});
Complete PowerShell examples are pending.
Here's the Python code:
def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
message = req.get_json()
signalROutput.set(json.dumps({
'target': 'newMessage',
'arguments': [ message ]
}))
@FunctionName("sendMessage")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRMessage sendMessage(
@HttpTrigger(
name = "req",
methods = { HttpMethod.POST },
authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req) {
SignalRMessage message = new SignalRMessage();
message.target = "newMessage";
message.arguments.add(req.getBody());
return message;
}
You can send a message only to connections that have been authenticated to a user by setting the user ID in the SignalR message.
[FunctionName("SendMessage")]
public static Task SendMessage(
[HttpTrigger(AuthorizationLevel.Anonymous, "post")]object message,
[SignalR(HubName = "hubName1")]IAsyncCollector<SignalRMessage> signalROutput)
{
return signalROutput.AddAsync(
new SignalRMessage
{
// the message will only be sent to this user ID
UserId = "userId1",
Target = "newMessage",
Arguments = new [] { message }
});
}
Here's binding data in the function.json file:
Example function.json:
{
"type": "signalR",
"name": "signalROutput",
"hubName": "hubName1",
"connectionStringSetting": "<name of setting containing SignalR Service connection string>",
"direction": "out"
}
Complete PowerShell examples are pending.
Here's the Python code:
def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
message = req.get_json()
signalROutput.set(json.dumps({
#message will only be sent to this user ID
'userId': 'userId1',
'target': 'newMessage',
'arguments': [ message ]
}))
@FunctionName("sendMessage")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRMessage sendMessage(
@HttpTrigger(
name = "req",
methods = { HttpMethod.POST },
authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req) {
SignalRMessage message = new SignalRMessage();
message.userId = "userId1";
message.target = "newMessage";
message.arguments.add(req.getBody());
return message;
}
const { app, output } = require('@azure/functions');
const signalR = output.generic({
type: 'signalR',
name: 'signalR',
hubName: 'hub',
connectionStringSetting: 'AzureSignalRConnectionString',
});
app.http('sendToUser', {
methods: ['GET'],
authLevel: 'anonymous',
extraOutputs: [signalR],
handler: (request, context) => {
context.extraOutputs.set(signalR, {
"target": "newMessage",
"arguments": [request.body],
"userId": "userId1",
});
}
});
You can send a message only to connections that have been added to a group by setting the group name in the SignalR message.
[FunctionName("SendMessage")]
public static Task SendMessage(
[HttpTrigger(AuthorizationLevel.Anonymous, "post")]object message,
[SignalR(HubName = "hubName1")]IAsyncCollector<SignalRMessage> signalROutput)
{
return signalROutput.AddAsync(
new SignalRMessage
{
// the message will be sent to the group with this name
GroupName = "myGroup",
Target = "newMessage",
Arguments = new [] { message }
});
}
Here's binding data in the function.json file:
Example function.json:
{
"type": "signalR",
"name": "signalROutput",
"hubName": "hubName1",
"connectionStringSetting": "<name of setting containing SignalR Service connection string>",
"direction": "out"
}
const { app, output } = require('@azure/functions');
const signalR = output.generic({
type: 'signalR',
name: 'signalR',
hubName: 'hub',
connectionStringSetting: 'AzureSignalRConnectionString',
});
app.http('sendToGroup', {
methods: ['GET'],
authLevel: 'anonymous',
extraOutputs: [signalR],
handler: (request, context) => {
context.extraOutputs.set(signalR, {
"target": "newMessage",
"arguments": [request.body],
"groupName": "myGroup",
});
}
});
Complete PowerShell examples are pending.
Here's the Python code:
def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
message = req.get_json()
signalROutput.set(json.dumps({
#message will only be sent to this group
'groupName': 'myGroup',
'target': 'newMessage',
'arguments': [ message ]
}))
@FunctionName("sendMessage")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRMessage sendMessage(
@HttpTrigger(
name = "req",
methods = { HttpMethod.POST },
authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req) {
SignalRMessage message = new SignalRMessage();
message.groupName = "myGroup";
message.target = "newMessage";
message.arguments.add(req.getBody());
return message;
}
SignalR Service allows users or connections to be added to groups. Messages can then be sent to a group. You can use the SignalR
output binding to manage groups.
Specify GroupAction
to add or remove a member. The following example adds a user to a group.
[FunctionName("addToGroup")]
public static Task AddToGroup(
[HttpTrigger(AuthorizationLevel.Anonymous, "post")]HttpRequest req,
ClaimsPrincipal claimsPrincipal,
[SignalR(HubName = "hubName1")]
IAsyncCollector<SignalRGroupAction> signalRGroupActions)
{
var userIdClaim = claimsPrincipal.FindFirst(ClaimTypes.NameIdentifier);
return signalRGroupActions.AddAsync(
new SignalRGroupAction
{
UserId = userIdClaim.Value,
GroupName = "myGroup",
Action = GroupAction.Add
});
}
Note
In order to get the ClaimsPrincipal
correctly bound, you must have configured the authentication settings in Azure Functions.
Here's binding data in the function.json file:
Example function.json:
{
"type": "signalR",
"name": "signalROutput",
"hubName": "hubName1",
"connectionStringSetting": "<name of setting containing SignalR Service connection string>",
"direction": "out"
}
const { app, output } = require('@azure/functions');
const signalR = output.generic({
type: 'signalR',
name: 'signalR',
hubName: 'hub',
connectionStringSetting: 'AzureSignalRConnectionString',
});
// The following function adds a user to a group
app.http('addUserToGroup', {
methods: ['POST'],
authLevel: 'anonymous',
extraOutputs: [signalR],
handler: (request, context) => {
context.extraOutputs.set(signalR, {
"userId": req.query.userId,
"groupName": "myGroup",
"action": "add"
});
}
});
// The following function removes a user from a group
app.http('removeUserFromGroup', {
methods: ['POST'],
authLevel: 'anonymous',
extraOutputs: [signalR],
handler: (request, context) => {
context.extraOutputs.set(signalR, {
"userId": req.query.userId,
"groupName": "myGroup",
"action": "remove"
});
}
});
Complete PowerShell examples are pending.
The following example adds a user to a group.
def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
signalROutput.set(json.dumps({
'userId': 'userId1',
'groupName': 'myGroup',
'action': 'add'
}))
The following example removes a user from a group.
def main(req: func.HttpRequest, signalROutput: func.Out[str]) -> func.HttpResponse:
signalROutput.set(json.dumps({
'userId': 'userId1',
'groupName': 'myGroup',
'action': 'remove'
}))
The following example adds a user to a group.
@FunctionName("addToGroup")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRGroupAction addToGroup(
@HttpTrigger(
name = "req",
methods = { HttpMethod.POST },
authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req,
@BindingName("userId") String userId) {
SignalRGroupAction groupAction = new SignalRGroupAction();
groupAction.action = "add";
groupAction.userId = userId;
groupAction.groupName = "myGroup";
return action;
}
The following example removes a user from a group.
@FunctionName("removeFromGroup")
@SignalROutput(name = "$return", HubName = "hubName1")
public SignalRGroupAction removeFromGroup(
@HttpTrigger(
name = "req",
methods = { HttpMethod.POST },
authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Object> req,
@BindingName("userId") String userId) {
SignalRGroupAction groupAction = new SignalRGroupAction();
groupAction.action = "remove";
groupAction.userId = userId;
groupAction.groupName = "myGroup";
return action;
}
Both in-process and isolated worker process C# libraries use attribute to define the function. C# script instead uses a function.json configuration file.
The following table explains the properties of the SignalR
output attribute.
Attribute property | Description |
---|---|
HubName | This value must be set to the name of the SignalR hub for which the connection information is generated. |
ConnectionStringSetting | The name of the app setting or settings collection that contains the SignalR Service connection string, which defaults to AzureSignalRConnectionString . |
The following table explains the supported settings for the SignalROutput
annotation.
Setting | Description |
---|---|
name | Variable name used in function code for connection info object. |
hubName | This value must be set to the name of the SignalR hub for which the connection information is generated. |
connectionStringSetting | The name of the app setting or settings collection that contains the SignalR Service connection string, which defaults to AzureSignalRConnectionString . |
The following table explains the binding configuration properties that you set in the function.json file.
function.json property | Description |
---|---|
type | Must be set to signalR . |
direction | Must be set to out . |
name | Variable name used in function code for connection info object. |
hubName | This value must be set to the name of the SignalR hub for which the connection information is generated. |
connectionStringSetting | The name of the app setting or settings collection that contains the SignalR Service connection string, which defaults to AzureSignalRConnectionString . |
When you're developing locally, add your application settings in the local.settings.json file in the Values
collection.
For optimal security, your function app should use managed idenities when connecting to the Azure SignalR service instead of using a connection string, which contains a shared secret key. For more information, see Authorize requests to Azure SignalR Service resources with Microsoft Entra managed identities.
Events
Mar 17, 11 PM - Mar 21, 11 PM
Join the meetup series to build scalable AI solutions based on real-world use cases with fellow developers and experts.
Register now