Answer 1

TelentClient extends Telnet and Telnet extends SocketClient. If you see these classes, it will create VT100 connection. See the below code from TelnetClient.java.

 public TelnetClient() {
   /* TERMINAL-TYPE option (start)*/
   super ("VT100");
   /* TERMINAL-TYPE option (end)*/
   __input = null;
   __output = null;
 }

This will now create the super classes. See the code from Telnet.java class.

Telnet() {
      setDefaultPort(DEFAULT_PORT);
      _doResponse = new int[TelnetOption.MAX_OPTION_VALUE + 1];
      _willResponse = new int[TelnetOption.MAX_OPTION_VALUE + 1];
      _options = new int[TelnetOption.MAX_OPTION_VALUE + 1];
      optionHandlers = new TelnetOptionHandler[TelnetOption.MAX_OPTION_VALUE + 1];
}

The DEFAULT_PORT here is 23.

Now, see the connect method from SocketClient.java.

        public void connect(InetAddress host, int port)
                throws SocketException, IOException {
            _socket_ = _socketFactory_.createSocket(host, port);
            _connectAction_();
        }

This is creating a new Socket using DefaultSocketFactory, which is a TCP socket to specified Host and Port. In the connectAction method, its setting the timeout for the new socket.

Now, when we call disconnect, its first trying to close the socket.

public void disconnect() throws IOException {
            _socket_.close();
            _input_.close();
            _output_.close();
            _socket_ = null;
            _input_ = null;
            _output_ = null;
            _isConnected_ = false;
        }

Because you are able to close the Streams directly, so seems the problem with the socket itself.

This will be a TCP socket, and i don't know how Android behaves with TCP. Can you please check on that? Because this method is doing closing of 3 private members. OR may be the socket is already closed so that it can't close it again?

Hope this helps.

Thanks.

Answered by: Aida955 | Posted: 25-02-2022

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