23ChatServer.c

//Simple TCP Chat Server
//Taken from: http://www.tenouk.com/Module41.html
//Using select() for I/O multiplexing

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <termios.h>
#include <fcntl.h>

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

//Port we're listening on
#define PORT 2020

int main(int argc, char *argv[]) {
	fd_set master; 		//master file descriptor list
	fd_set read_fds; 	//temporary file descriptor list for select()
	struct sockaddr_in serveraddr;	//server address
	struct sockaddr_in clientaddr;	//client address
	int fdmax;			//maximum file descriptor number
	int listener;		//listening socket descriptor
	int newfd;			//newly accept()ed socket descriptor
	char buf[1024];		//buffer for client data
	int nbytes;
	int yes = 1;		//for setsockopt() SO_REUSEADDR, below
	unsigned int addrlen;
	int i, j;

	//clear the master and temporary file descriptor sets
	FD_ZERO(&master);
	FD_ZERO(&read_fds);

	//get a socket for listening on
	if((listener = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		perror("Server-socket() error lol!");
		exit(1);	//just exit lol!
	}
	printf("Server-socket() is OK...\n");

	//"address already in use" error message
	if(setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1)	{
		perror("Server-setsockopt() error lol!");
		exit(1);
	}
	printf("Server-setsockopt() is OK...\n");

	//bind
	serveraddr.sin_family = AF_INET;
	serveraddr.sin_addr.s_addr = INADDR_ANY;
	serveraddr.sin_port = htons(PORT);
	memset(&(serveraddr.sin_zero), '\0', 8);

	if(bind(listener, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) == -1) {
		perror("Server-bind() error lol!");
		exit(1);
	}
	printf("Server-bind() is OK...\n");

	//listen
	if(listen(listener, 10) == -1) {
		perror("Server-listen() error lol!");
		exit(1);
	}
	printf("Server-listen() is OK...\n");

	//add the listener to the master set
	FD_SET(listener, &master);
	//keep track of the biggest file descriptor
	fdmax = listener; 	//so far, it's this one

	//loop
	for(;;) {
		//copy it
		read_fds = master;

		if(select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1) {
			perror("Server-select() error lol!");
			exit(1);
		}
		//printf("Server-select() is OK...\n");

		//run through the existing connections looking for data to be read
		for(i = 0; i <= fdmax; i++) {
			if(FD_ISSET(i, &read_fds)) {
				//we got one...
				if(i == listener) {
					//handle new connections
					addrlen = sizeof(clientaddr);
					if((newfd = accept(listener, (struct sockaddr *)&clientaddr, &addrlen)) == -1) {
						perror("Server-accept() error lol!");
					} else {
						printf("Server-accept() is OK...\n");

						FD_SET(newfd, &master); //add to master set
						if(newfd > fdmax) {
							//keep track of the maximum
							fdmax = newfd;
						}
						printf("New connection from %s on socket %d\n", inet_ntoa(clientaddr.sin_addr), newfd);
					}
				} else {
					//handle data from a client
					if((nbytes = recv(i, buf, sizeof(buf), 0)) <= 0) {
						//got error or connection closed by client
						if(nbytes == 0)
							//connection closed
							printf("socket %d hung up\n", i);
						else
							perror("recv() error lol!");
						//close it...
						close(i);
						//remove from master set
						FD_CLR(i, &master);
					} else {
						//we got some data from a client
						printf("Socket %d sent %d bytes\n",i,nbytes);
						for(j = 0; j <= fdmax; j++)	{
							//send to everyone!
							if(FD_ISSET(j, &master)) {
								//except the listener and ourselves
								if(j != listener && j != i)	{
									if(send(j, buf, nbytes, 0) == -1)
										perror("send() error lol!");
									else
										printf("\tForwarded %d bytes to socket %d\n",nbytes,j);
								}
							}
						}
					}
				}
			}
		}
	}
	return 0;
}