how to handle net.connect's error callback when hostname is weird?

[espruino-discuss]

Posted at 2016-05-04 by ceremcem

Hi,

I found this conversation but I didn't find my answer in the replies.

When I try to connect to a valid server, my application works as expected and exchanges data. If I try to connect to an invalid server, for example net.connect({host: "hello", port: 123}, function () {...., then it hangs while trying to connect.

How can I implement a timeout or something in order to fall back to a default server?

[espruino-discuss]

Posted at 2016-05-04 by ceremcem

OK, I've succeded with the following code:

connect-to-server = !->
    csock = null
    connect-to = (server) ->
        console.log "trying to connect to the server...", server
        csock := net.connect server, (socket) !->
            console.log "client connected. "
            socket.on \data, (data) !->
                do-something!
            socket.on \end, !->
                console.log "client disconnected..."

    connect-to first-server
    <- sleep 10_000ms
    if csock.sckt is void
        console.log "timed out, trying default server..."
        connect-to default-server
    else
        console.log "Connected to the first server correctly, not trying default..."

...Javascript:

var connectToServer;
connectToServer = function(){
  var csock, connectTo;
  csock = null;
  connectTo = function(server){
    console.log("trying to connect to the server...", server);
    return csock = net.connect(server, function(socket){
      console.log("client connected. ");
      socket.on('data', function(data){
        doSomething();
      });
      socket.on('end', function(){
        console.log("client disconnected...");
      });
    });
  };
  connectTo(firstServer);
  sleep(10000, function(){
    if (csock.sckt === void 8) {
      console.log("timed out, trying default server...");
      return connectTo(defaultServer);
    } else {
      return console.log("Connected to the first server correctly, not trying default...");
    }
  });
};

[gfwilliams]

Posted at 2016-05-04 by @gfwilliams

You might be able to do:

csock = net.connect(server, function(socket){
});
csock.on("error", function(info) { ... });

I think socket connections should time out eventually - it might take maybe 30 seconds or a minute though?

[espruino-discuss]

Posted at 2016-05-04 by DrAzzy

Yeah - it's an awkwardly long timeout. So if you're updating it too often (eg, in an interval), if the server goes down, it hoses everything.

That's why I can't turn on some of the lights in my room if the webserver on the shelf in the living room isn't running.