Very simple server in C

Question

As one of the assigments we have to implement very simple server in C with some clients. The idea is that using system V IPC queues we create one queue where clients register and then for every client there is one queue with messages. I am wondering a bit about server part. Should I have something like this:

while(1)
{
  //some queue using code
  sleep(100);
}

so for every time interval I check every queue and do what I have to do, or maybe I should use signals to inform server that at least one of the queues is ready to be managed.

How is it done in normal servers, do they have some time interval after which they check everything they need to do or there is more proper way to do this?

Typical networking code in C is usually done with something like [`select()`](http://stackoverflow.com/questions/4171270/select-function-in-socket-programming), which is event-based. Here is a pretty good guide (at least when I used it): http://beej.us/guide/bgnet/ — wkl, May 10 '12 at 13:14
I'm not sure about that (I haven't touched the System V stuff in probably 7 years), but part of the guide I linked above also discusses the use of System V Queues: http://beej.us/guide/bgipc/output/html/multipage/mq.html Although I think in your case, what you would do is have clients connect and select on their socket/descriptors, and manage a queue for them (instead of `select()`-ing on the queue). — wkl, May 10 '12 at 13:24
@Andna: `select(), poll() and epoll()` work on queues only on linux. This is not portable to any other UNIX system. see [mq_overview manpage](http://linux.die.net/man/7/mq_overview). — dwalter, May 10 '12 at 13:31

score 3 · Accepted Answer · answered May 11 '12 at 21:08

You have to do something along the lines of this:

This is a very basic answer, and needs definitions and prototypes to be in place, however that should give you a basic select, example.

this code works both on freebsd, ubuntu, and my windows computer (Given you have the correct headers) Also its been minified and some definitions removed, suck as socket descriptor defs because those are pretty much - it is what it is.

struct timeval timeout;
int rc
fd_set wfdset,rfdset,errfdset;
//Do some checks put them in either read fdset or write fdset or error fdset 
FD_SET (socket_sd, &rfdset);
timeout.tv_sec = 0;
timeout.tv_usec = 250 * 1000;
rc = select (maxfds + 1, &rfdset, &wfdset, NULL, &timeout);
//loop through the sockets and read from them at this point.

Select is portable to Win32 as well as UNIX, though it isn't the recommended choice if you are doing any heavy lifting on sockets in unix IE: FreeBSD. use kqueue or epoll or the like if you need to get deeper and have greater management of your sockets.

Very simple server in C

1 Answers1