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I’m trying to connect to a device over TCP socket, write data and read response from socket. I made simple testing with c#, which works as expected.
C# code, that works well:

using (TcpClient client = new TcpClient(terminal.server_IP, terminal.port))
        {
            try
            {
                using (NetworkStream stream = client.GetStream())
                {
                    try
                    {
                        stream.ReadTimeout = 5000;

                        byte[] msg = new byte[10];
                        msg[0] = 1;
                        msg[1] = 1;
                        msg[2] = 0;
                        msg[3] = 5;
                        msg[4] = 70;
                        msg[5] = 82;
                        msg[6] = 82;
                        msg[7] = 84;
                        msg[8] = 67;
                        msg[9] = 81;

                        stream.Write(msg, 0, msg.Length);

                        int i = 0;
                        while (!stream.DataAvailable && i < 5)
                        {
                            await Task.Delay(100);
                            i++;
                        }

                        byte[] data = new byte[4096];
                        int bytes = stream.Read(data, 0, data.Length);
                        msg = new byte[bytes];
                        string tst = Encoding.GetEncoding("Windows-1250").GetString(data, 2, data[1]);
                    }
                    finally
                    {
                        stream.Close();
                    }
                }
            }
            finally
            {
                client.Close();
            }
        }

i need to transform this into a flutter application, i made the code, where the data don’t get back to listen.
Flutter code:

try {
  socket?.destroy();
  socket = await Socket.connect(serverIP, serverPort).catchError((error) {
    print('error $e');
  });

  socket!.listen((data) {
    print('data');
  }, onError: (e) {
    print('error');
    socket!.destroy();
  }, onDone: () {
    print('done');
    socket!.destroy();
  }, cancelOnError: false);

  List<int> message = [1, 1, 0, 5, 70, 82, 82, 84, 67, 81];
  socket!.write(message);
} catch (e) {
  print('errors: $e');
}

it don’t throws any errors, everyhing runs, but i can’t read the data from the device. Any advice what i’m doing wrong?

2

Answers


  1. Chosen as BEST ANSWER

    So, after a couple of days tying, i figured that the problem was sthe socket!.write(message). I replaced it with socket!.add(message);, not it works as expected.

    Leaving it here for evidence, to save time for someone in the future who has the same problems.


  2. I’m not sure if this is gonna work with you honestly, but it might.

    I tried to integrate web socket before in a flutter app knowing that the backend was made with laravel, and the only package that worked for me was web_socket_channel.
    i hope it work

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