Question

Looking at the code:

private static void send(final Socket socket, final String data) throws IOException {
    final OutputStream os = socket.getOutputStream();
    final DataOutputStream dos = new DataOutputStream(os);
    dos.writeUTF(data);
    dos.flush();
}

can I be sure that calling this method either throws IOException (and that means that I’d better close the socket), or, if no exceptions are thrown, the data I send is guaranteed to be fully send? Are there any cases when I read the data on the other endpoint, the string I get is incomplete and there are no exception?

Answer 1

There is a big difference between sent and received. You can send data from the application successfully, however it then passes to

• the OS on your machine
• the network adapter
• the switch(s) on the network
• the network adapter on the remote machine
• the OS on the remote machine
• the application buffer on the remote machine
• whatever the application does with it.

Any of these stages can fail and your sender will be none the wiser.

If you want to know the application has received and processed the data successfully, it must send you back a message saying this has happened. When you receive this, then you know it was received.