Error: Specified protocol was not requested by the client. Flutter and Node Web Socket

Question

I have a flutter code and node backend. I want to communicate via socket. So I intiailize a socket client in flutter and socket server in node. But when I try to connect this client it creates an error in my node server that is

Error: Specified protocol was not requested by the client.

Flutter code

...

void initState() {
    super.initState();
    LogEntryRepository repository = new LogEntryRepository();
    getLogEntries(repository);
    var s = IOWebSocketChannel.connect("ws://192.168.0.107:8080/", protocols: ['echo-protocol']);
    print(s.protocol);
    print(s.closeReason);
}

...

Node Code

#!/usr/bin/env node
var WebSocketServer = require('websocket').server;
var http = require('http');

var server = http.createServer(function(request, response) {
    console.log((new Date()) + ' Received request for ' + request.url);
    response.writeHead(404);
    response.end();
});
server.listen(8080, "0.0.0.0", function() {
    console.log((new Date()) + ' Server is listening on port 8080');
});

wsServer = new WebSocketServer({
    httpServer: server,
    // You should not use autoAcceptConnections for production
    // applications, as it defeats all standard cross-origin protection
    // facilities built into the protocol and the browser.  You should
    // *always* verify the connection's origin and decide whether or not
    // to accept it.
    autoAcceptConnections: false
});

function originIsAllowed(origin) {
  // put logic here to detect whether the specified origin is allowed.
  return true;
}

wsServer.on('request', function(request) {
    if (!originIsAllowed(request.origin)) {
      // Make sure we only accept requests from an allowed origin
      request.reject();
      console.log((new Date()) + ' Connection from origin ' + request.origin + ' rejected.');
      return;
    }

    var connection = request.accept('echo-protocol', request.origin);
    console.log((new Date()) + ' Connection accepted.');
    connection.on('message', function(message) {
        if (message.type === 'utf8') {
            console.log('Received Message: ' + message.utf8Data);
            connection.sendUTF(message.utf8Data);
        }
        else if (message.type === 'binary') {
            console.log('Received Binary Message of ' + message.binaryData.length + ' bytes');
            connection.sendBytes(message.binaryData);
        }
    });
    connection.on('close', function(reasonCode, description) {
        console.log((new Date()) + ' Peer ' + connection.remoteAddress + ' disconnected.');
    });
});

This is my Node code. The error occurs from the line request.accept('echo-protocol', request.origin);

Richard Heap · Accepted Answer · 2019-07-26 20:04:11Z

2

It seems that IoWebSocketChannel ignores the protocols parameter.

Try constructing it as:

var ws = await WebSocket.connect("ws://192.168.0.107:8080/", protocols: ['echo-protocol']);
var s = IoWebSocketChannel(ws);

(You must do this in an async method as it requires await to get the underlying web socket.)

answered Jul 26, 2019 at 20:04

Richard Heap

52.1k11 gold badges143 silver badges118 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Nimish Bansal Over a year ago

Thanks a lot. It worked. But why they have mentioned protocols as a paremeter if they simply ignored it.

Richard Heap Over a year ago

I think it's a bug. As the workaround worked, that sort of proves it. Maybe create an issue for that package.

Collectives™ on Stack Overflow

Error: Specified protocol was not requested by the client. Flutter and Node Web Socket

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related