please help with select on linux sockets

[mushy]

The code compiles and runs ok, but when i connect to it using netcat nothing happens, well i think netcat connects because it starts running through the for loop.

However when i type something in netcat to send it does not appear on the screen
I added in error checking, all it does is repeadly prints to the screen

select running ok.......
crap
crap
crap
select running ok......
crap
crap
crap

etc

So FD_ISSET(count,&read_fds)

must not be working properly as its ment to return a non zero when it matches them.

FD_SET(sock,&master);
	fdmax = sock;

	//infinate loop to run though connections
	int count;
	int j;
	for(;;){

	read_fds = master;
	if(select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1){

		Die("Error: Select Malfunctions");
		

	}
	printf("select running ok...\n");
	//select is ok - read through fd's looking for data
	
	for(count = 0; count < fdmax; count++){

		if(FD_ISSET(count,&read_fds) != 0){
		
			//something set read it
			printf("Something is set\n");
			if(count == sock)
			{
				//new connection
				int client_length = sizeof(client_address);
				if(connected_socket = accept(sock,(struct sockaddr *) &client_address, &client_length)== -1){
				Die("Error Couldn't accept connection\n");
			;

				}
				printf("Connection Accepted\n");

				//added new connection ad to fd
				FD_SET(connected_socket,&master);
				if(connected_socket > fdmax){

					fdmax = connected_socket;
				}

				printf("\n\nNew connection From %s on socket %d",inet_ntoa(client_address.sin_addr), connected_socket);
			
			}

			
				

			

		 }//if statement checking for fd isset

	         else{//nothing
			printf("crap\n");
			}
		

	}//for loop for fd_sets


	}//eternal for loop

[MK27]

I can pretty much promise everything in the API works properly, since most of the internet depends on linux sockets.

However, I'll concurr it is not always easy to get it to work. I'm not sure exactly what your problem is, but I do see a potential design flaw.

fdmax = sock;

I presume that is the server socket, since it's what you use with accept().

	for(count = 0; count < fdmax; count++){

Why do this? fds 0-2 are stdin, stdout, and stderr. You should not be polling them, or polling fd's willy-nilly. You poll only the fd's which are actually part of one of your sets. [edit: actually I guess you aren't polling them...anyway]

Now, you do advance fdmax to include new sockets:

fdmax = connected_socket;

Chances are you could just count from sock up to fdmax, but I still think you need to maintain an array of open descriptors (possibly you could examine how the fd_set bit array works and get it from there). Your method of setting this number is also very sloppy:

if(select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1){

That should be the actual number of readable sockets, not the number of the highest one+1. There is only one socket in read_fds initially, but you are telling select there are at least 4.

Of course, that maybe does not explain why the code isn't working; sloppiness is not complete condemnation

You could try a little more debugging:

fprintf(stderr,"read_fds: %ld\n",read_fds);
for(count = 0; count < fdmax; count++){
		if(FD_ISSET(count,&read_fds) != 0){
                        fprintf(stderr,"\t-->%d\n",count);

[Salem]

> if(connected_socket = accept(sock,(struct sockaddr *) &client_address, &client_length)== -1)
Watch your precedence rules.

You've written
if ( a = (b == c) )

You want
if ( (a = b) == c )

[itCbitC]

In the statement below

if(FD_ISSET(count, &read_fds) != 0)   /* sock is a file descriptor, not count */