I wrote a program that creates a TCP and UDP socket in C and starts both servers up. The goal of the application is to monitor requests over the TCP socket as to what UDP packets to send it (i.e. monitor for something like “0x01 0x02” and if I see it, then have the UDP server parse the payload, and forward it over to the TCP server for processing). The problem is, the UDP server will be busy keeping another device up, literally sending thousands of packets back and forth with this device. So what is the best way to continuously monitor requests from the TCP server, but send it certain payloads from the UDP server when requested since the UDP server will be busy?
I looked into pthreads with semaphores and/or mutex (not sure all the socket operations are thread safe, though, and if this is the right way to approach it) as well as fork / pipe. Forking the UDP server off as a child process seems easy enough, but I don’t see exactly how I would be passing the kind of data I need among both servers (need request data from TCP and payload data from the UDP).
Firstly, would it make sense to put these two servers into one program? If so, you won’t have to communicate between processes, and the whole logic becomes substantially easier. You will have to think about doing asynchronous input and output, and the
select()function is designed for just this. There will be many explanations around on how to do this, and a quick look finds this page.However, if you must have two separate processes, then you will need to choose a mechanism for inter-process communication, of which there are several, and your choice will be affected by your operating system. A pipe, if available, might be suitable, as might a Unix named pipe. Or you could look into third-party message passing frameworks, or just use shared memory and/or semaphores (but be very careful!).