How to check if a socket is connected/disconnected in C#?

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As Paul Turner answered Socket.Connected cannot be used in this situation. You need to poll connection every time to see if connection is still active. This is code I used:

bool SocketConnected(Socket s)
{
    bool part1 = s.Poll(1000, SelectMode.SelectRead);
    bool part2 = (s.Available == 0);
    if (part1 && part2)
        return false;
    else
        return true;
}

It works like this:

  • s.Poll returns true if
    • connection is closed, reset, terminated or pending (meaning no active connection)
    • connection is active and there is data available for reading
  • s.Available returns number of bytes available for reading
  • if both are true:
    • there is no data available to read so connection is not active

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