websocketd ~main

Websocket Server

This is a dubization of George Zakhour web socket server

Usage

To start, every connected peer receives an ID whose type is PeerID.

To implement a protocol, you start by creating a subclass of WebSocketServer.

And you will have to implement four methods:

• override void onOpen(PeerID id, string path) which is executed every time a client connects to the websocket server. The id argument is the generated ID of the newly connected client, the path argument is the path the client connects to.
• override void onClose(PeerID id) which is executed everytime a client disconnects.
• override void onTextMessage(PeerID id, string msg) which is executed every time a TEXT message from a client id is received.
• override void onBinaryMessage(PeerID id, ubyte[] msg) which is executed every time a BINARY message from a client id is received.

To run the server you need to execute the run(ushort port, size_t maxConnections)() method on the server instance. The port template argument is the port the server needs to run, and the maxConnections template argument is the maximum number of allowed connections. When the maximum number of connections is reached every new connection will be denied.

To send a message to a peer whose id is id, you can use sendText(PeerID id, string msg) or the sendBinary(PeerID id, ubyte[] msg) methods.

Examples

Some examples can be found in test_server.d which are recreated here.

Echo server

class EchoWebsocketServer : WebSocketServer {

    override void onOpen(PeerID s, string path) {}
    override void onClose(PeerID s) {}

    override void onBinaryMessage(PeerID id, ubyte[] msg) {
        sendBinary(id, msg);
    }

    override void onTextMessage(PeerID id, string msg) {
        sendText(id, msg);
    }
}

To run echo version:

$ cd examples
$ dub run -cecho

In order to test we can use websocat

$ websocat ws://127.0.0.1:10301

If you use nginx you can create a proxy:

  location /ws {
        proxy_pass http://127.0.0.1:10301;
  }

so:

$ websocat ws://127.0.0.1/ws

Broadcasting server based on the connected path

Clients can subscribe to the channel xyz by connecting to ws://example.com/xyz. Clients connected to another channel (eg. abc) will not receive messages from other channels (eg. xyz).

class BroadcastServer : WebSocketServer {

    private string[PeerID] peers;

    override void onOpen(PeerID s, string path) {
        peers[s] = path;
    }

    override void onClose(PeerID s) {
        peers.remove(s);
    }

    override void onTextMessage(PeerID src, string msg) {
        send!(sendText, typeof(msg))(src, msg);
    }

    override void onBinaryMessage(PeerID src, ubyte[] msg) {
        send!(sendBinary, typeof(msg))(src, msg);
    }

    private void send(alias sender, T)(PeerID src, T msg) {
        string srcPath = peers[src];
        foreach (id, path; peers)
            if (id != src && path == srcPath)
                sender(id, msg);
    }

}

To run broadcast version:

$ cd examples
$ dub run -cbroadcast

Running the server with TLS

The server natively does not support TLS. However if you use nginx you can create a proxy and use nginx for TLS. Here's an example of an nginx configuration.

upstream websocketservers {
    server localhost:10301; # 10301 being the port websocket-d-server runs on
}

server {
    server_name example.com;
    # ...

    location /<path> {
        proxy_pass http://websocketservers;
    }

    listen 443 ssl;
    # ...
}

Then a client can connect via wss://example.com/