Publish Subscribe

Basics

Once connected you can publish messages by calling the ISubscriber.Publish method:

// grab an instance of an ISubscriber
var subscriber = connection.GetSubscriber();

// publish a message to the 'chat' channel
subscriber.Publish("chat", "This is a message")

Consumers can subscribe to the channel using the ISubscriber.Subscribe method. Messages sent by the publisher will be handled by the handler passed to this method.

// grab an instance of an ISubscriber
var subscriber = connection.GetSubscriber();

// subscribe to a messages over the 'chat' channel
subscriber.Subscribe("chat", (channel, message) => {
    // do something with the message
    Console.WriteLine((string)message);
});

Complex Data (JSON)

You can broadcast more complex messages by serializing the payload before you publish it:

// definition of a message
public class ChatMessage
{
    public Guid Id { get; set; }
    public string User { get; set; }
    public string Text { get; set; }
}

// grab an instance of an ISubscriber
var subscriber = connection.GetSubscriber();

var message = new ChatMessage
{
    Id = Guid.NewGuid(), 
    User = "User 1234", 
    Text = "Hello World!"
};

// serialize a ChatMessage
// this uses JIL to serialize to JSON
var json = JSON.Serialize(message);

// publish the message to the 'chat' channel
subscriber.Publish("chat", json)

The subscriber then needs to deserialize the message:

// grab an instance of an ISubscriber
var subscriber = connection.GetSubscriber();

// subscribe to messages over the 'chat' channel
subscriber.Subscribe("chat", (channel, json) => {
    var message = JSON.Deserialize<ChatMessage>(json);

    // do something with the message
    Console.WriteLine($"{message.User} said {message.Text}");
});

Complex Data (Protobuf)

StackExchange.Redis also supports sending bytes over the pub/sub channel, here we use protobuf-net to serialize our message to a byte array before sending it:

// definition of a message (marked up with Protobuf attributes)
[ProtoContract]
public class ChatMessage
{
    [ProtoMember(1)]
    public Guid Id { get; set; }
    [ProtoMember(2)]
    public string User { get; set; }
    [ProtoMember(3)]
    public string Text { get; set; }
}

// grab an instance of an ISubscriber
var subscriber = connection.GetSubscriber();

var message = new ChatMessage
{
    Id = Guid.NewGuid(), 
    User = "User 1234", 
    Text = "Hello World!"
};

using (var memoryStream = new MemoryStream())
{
    // serialize a ChatMessage using protobuf-net
    Serializer.Serialize(memoryStream, message);

    // publish the message to the 'chat' channel
    subscriber.Publish("chat", memoryStream.ToArray());
}

Again the subscriber needs to deserialize the message upon receipt:

// grab an instance of an ISubscriber
var subscriber = connection.GetSubscriber();

// subscribe to messages over the 'chat' channel
subscriber.Subscribe("chat", (channel, bytes) => {
    using (var memoryStream = new MemoryStream(bytes))
    {
        var message = Serializer.Deserialize<ChatMessage>(memoryStream);

        // do something with the message
        Console.WriteLine($"{message.User} said {message.Text}");
    }
});