Dart: How can I catch a SocketException from a socket.add() call?

Question

I am developing an Android app where I need to have a TCP socket open. This is done using a ServerSocket that receives a connection attempt and creates a Socket object. This object is stored in a Socket? variable.

It is expected for the other end of the socket to lose connection. When I try to send the next message I get

E/flutter (29620): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] 
Unhandled Exception: SocketException: Broken pipe (OS Error: Broken pipe, errno = 32), 
address = 0.0.0.0, port = 9000

which is expected. For this reason I put the socket.add call in a try-catch block like so:

if (socket != null) {
  try {
    socket?.add(msg);
  } on SocketException {
    if (kDebugMode) {
      print("Connection closed");
    }
    socket = null;
    /* ... */
  }
} else {
  if (kDebugMode) {
    print("Socket disconnected");
  }
}

But this doesn't print "Connection closed" and results in the error above.

But, if I change the socket?.add(msg); line into throw const SocketException("test");, "Connection closed" is printed as expected. I also tried changing the on SocketException to on Exception or catch(_) but the exception coming from the send is always uncaught.

What am I missing or doing wrong?