Question

I have long-lasting TCP connection between two computers (second not under my control). Second computer can send FIN flag at every moment, and first must close connection corrent (send FIN flag back to second computer).

How can I know that the second computer sending a FIN flag and when I must cause socket.close() method of my Java application?

Answer 1

Normally, you have to read the connection and when this returns -1 for EOF or an appropriate IOException, you can close the connection. Note: SocketTimeoutException doesn’t mean the connection is closed.

an example.

boolean ok = false;
try {
  int b = in.read();
  ok = b >= 0;
  if (!ok)
     throw new EOFException();
} finally {
  if (!ok)
     in.close();
}