sockets, UDP, using select()

Pres · 08-21-2003, 11:43 AM

I am using select() both on my server and clients, prior to any recvfrom() or sendto() ... testing read and write flags accordingly.

Am I doing the right thing here ? Any info greatly appreciated.

Mohsen · 08-21-2003, 02:26 PM

See:

Code:

    ....
    fd_set rfds;
    struct timeval tv;
    struct sockaddr_in client;
    int a=sizeof(client);
    tv.tv_sec=0;
    tv.tv_usec=0;
    FD_ZERO(&rfds);
    FD_SET(fd,&rfds);
    while (select(fd+1,&rfds,0,0,&tv))
    {
        if ((l=recv_packet(packet,256,(struct sockaddr*)(&client),&a,0,0,&s))==-1)
            return;

        last_packet_came=get_time();
 
        switch(*packet) {
           .....
        }

The code I put here, is a part of the main server.c loop of the game 0verkill-0.16. As you can see the author explicitly callled select, before receiving data from client(s). recv_packet is something implimented by recvfrom plus some crc checks (it's a local function). That `while' you can see, is the main loop of the server. It means till when something is sent, do the cycle (clear?). FD_XXX are all macros, for example FD_SET as far as I know, is for adding a socket file descriptor to your fd set. You can find more details on man pages.

shishir · 08-22-2003, 05:19 AM

man select_tut is a great place to start with the use of select ..and further..it contains sample code also..
so it will explain the stuff in great detail

Pres · 08-22-2003, 10:41 AM

Thanks fellas, I was a little bit distraught about this but as it turns out things are under control. Situation was nothing at all to do with select() but more to do with other buggy parts of code. Fixed now

and against all expectations, all apparently working.