Question

Now, I’m interested to know – if I have a program of mine connection to a Server through TCP and the server sends a message to my program, but I am sending UDP packets at the same time, will the TCP packet get to me? Everything is in one class!

Thanks for your help!

Answer 1

Your question is actually on the border of several issues that all network application programmers must know and consider.

First of all: all data received from the network is stored in operating system’s internal buffer, where it awaits to be read. The buffer is not infinite, so if you wait long enough, some data may be dropped. Usually the chunks of data that are written there are single packets, but not always. You can never make any assumptions of how much data will be available for reading in TCP/IP communication. In UDP, on the other hand, you must always read a single packet, otherwise the data will be lost. You can use recvfrom to read UDP packets and I suggest using it.

Secondly: using blocking and non-blocking approach is one of the most important decisions for your network app. There is a lot of information about it in the Internet: C- Unix Sockets – Non-blocking read , what is the definition of blocking read vs non- blocking read? or a non-blocking tutorial.

As for threads: threads are never required to write a multiple connection handler application. Sometimes they will simplify your code, sometimes they will make it run faster. There are some well-known programming patterns for using threads, like handling each separate connection in a separate thread. More often than not, especially for an inexperienced programmer, using threads will only be a source of strange errors and headaches.

I hope that my post answers your question and addresses the discussion I’ve been having below another answer.