I am trying to send a message over a TCP socket at a regular interval (every second). Sometimes the full message will not be sent or two-four messages will be stacked and sent at once. I have if statements for if the return value is 0 or < 0, but those are never true. I tried the obvious approach of checking the exact return value of send() to see if less or more bytes were sent. It just returns the number that I specify in the parameter to send (which makes sense if send blocks until it sends that much), even if less bytes are sent. So is there an accurate way to say "was the right size packet sent? no? - do something"?
TCP provides a reliable stream of bytes, there's no message boundary. If you need to know the length of the message you have to build this into the protocol, eg: send every message with a 2 byte header which specifies the message length.