Socket Programming, Server w/ Multiple Clients in C - c

Question

I am running into some problem with my server. I am trying to reading inputs from multiple clients but I can only do it one at a time. I think my server's code does not have an issue. So I assume that my local clients are the ones that are actually at fault here. Are each clients exactly the same as the other if I want to handle multiple clients with different sockets. or are they different in some ways?
What do you guys think?
Server.c
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>
#include <stdlib.h>
//char *socket_path = "./socket";
char *socket_path = "\0hidden";
int main(int argc, char *argv[]) {
struct sockaddr_un addr;
//max client sockets
int max_sd, sd, i, client_socket[3], activity;
char buf[100];
int fd,cl,rc;
fd_set readfds;
if (argc > 3) socket_path=argv[3];
//establish socket
if ( (fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
perror("socket error");
exit(-1);
}
//establish socket name
memset(&addr, 0, sizeof(addr));
addr.sun_family = AF_UNIX;
strncpy(addr.sun_path, socket_path, sizeof(addr.sun_path)-1);
unlink(socket_path);
//bind socket
if (bind(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
perror("bind error");
exit(-1);
}
//listen to the socket
if (listen(fd, 5) == -1) {
perror("listen error");
exit(-1);
}
while (1) {
//clear the scoket set
FD_ZERO(&readfds);
//add fd socket to set
FD_SET(fd, &readfds);
max_sd = fd;
//add child sockets to the set
for(i = 0; i < 3; i++) {
sd = client_socket[i];
if(sd > 0) {
FD_SET( sd, &readfds);
}
if(sd > max_sd) {
max_sd = sd;
}
}
//wait for an activity from a socket
activity = select(max_sd + 1, &readfds,NULL, NULL,NULL);
if((activity < 0) && (errno!=EINTR)) {
printf("select");
}
if(FD_ISSET(fd, &readfds)) {
if ( (cl = accept(fd, NULL, NULL)) == -1) {
perror("accept error");
continue;
}
while ( (rc=read(cl,buf,sizeof(buf))) > 0) {
printf("read %u bytes: %.*s\n", rc, rc, buf);
}
if (rc == -1) {
perror("read");
exit(-1);
}
else if (rc == 0) {
printf("EOF\n");
close(cl);
}
}
}
return 0;
}

Answer 1

What?
//wait for an activity from a socket
activity = select(max_sd + 1, &readfds,NULL, NULL,NULL);
if((activity < 0) && (errno!=EINTR)) {
printf("select");
}
if(FD_ISSET(fd, &readfds)) {
if ( (cl = accept(fd, NULL, NULL)) == -1) {
Accepting a connection...
perror("accept error");
continue;
}
while ( (rc=read(cl,buf,sizeof(buf))) > 0) {
printf("read %u bytes: %.*s\n", rc, rc, buf);
}
Blocking read until there is no error... (with incorrect printf)
if (rc == -1) {
perror("read");
exit(-1);
}
else if (rc == 0) {
printf("EOF\n");
close(cl);
}
Incorrect, but assuming no real errors means reading till the other party closes their side.
With this in mind, how was this supposed to support several clients at once?
Read this: http://www.kegel.com/c10k.html

Answer 2

I don't know how sockets work in C, but I've been working on some Java programs, and the solution to your problem, in java, is to provide a separate thread on the server for each client. Each time a client connects to the server, you start a thread that will serve that client. A fork will help maybe.