TCP in C Programming

Question

I want to know how a client or server gets an acknowledgement packet from a client or server after sending a packet in TCP Channel in C programming.

Why don't I need to handle this in code? How exactly does the client receive the acknowledgement packet, if it sends a data packet to server? Does this happen internally?

Answer 1

The TCP protocol is designed to provide a stream protocol. The typical programming interface is the socket interface where you can give a chunk of data that the protocol stack will transfer to the receiver. The actual implementation hides when the data has been queued in the receiving protocol stack or has been handed off to the receiving application. You would have make this distinction.

Sou what you apparently want is a signal mechanism to know, that and when the client has read the data from the protocol stack. This can be done by designing and implementing a protocol on top of the TCP protocol. When one side doesn't have to send meaningful data it sends a heartbeat message. This message indicates that the TCP connection is still alive.

Regarding your questions:

• Why don't I need to handle this in code? Because the underlying layer has it done for your.

• How exactly does the client receive the acknowledgement packet, if it sends a data packet to server? You don't need to care as long as you don't need a heartbeat. TCP provides you a stream interface similar like the interface for file I/O. You don't ask, when the data has left the disk cache, do you? When you start to re-implement internas you will have to define what about reassemblies, Nagle-algorithm and many other nasty things. Never implement TCP if you have another choice.

• Does this happen internally? Yes, fortunately.