#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

/* port we're listening on */

#define PORT 2020

int main(int argc, char *argv[])
{

	argc = argc;

	/* master file descriptor list */
	fd_set master;
	/* temp file descriptor list for select() */
	fd_set read_fds;
	/* server address */
	struct sockaddr_in serveraddr;
	/* client address */
	struct sockaddr_in clientaddr;

	/* maximum file descriptor number */
	int fdmax;
	/* listening socket descriptor */
	int listener;
	/* newly accept()ed socket descriptor */
	int newfd;
	/* buffer for client data */
	char buf[1024];
	int nbytes;

	/* for setsockopt() SO_REUSEADDR, below */
	int yes = 1;
	socklen_t addrlen = 0;
	int i, j;

	/* clear the master and temp sets */
	FD_ZERO(&master);
	FD_ZERO(&read_fds);

	/* get the listener */
	if((listener = socket(AF_INET, SOCK_STREAM, 0)) == -1)
	{
		perror("Server-socket()");
		exit(1);
	}

	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()");
		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()");
		exit(1);
	}
	printf("Server-bind() is OK...\n");

	/* listen */
	if(listen(listener, 10) == -1)
	{
		perror("Server-listen()");
		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()");
			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()");
					}
					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("%s: New connection from %s on socket %d\n"
								, argv[0], 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("%s: socket %d hung up\n", argv[0], i);

						else
							perror("recv()");

						/* close it... */
						close(i);
						/* remove from master set */
						FD_CLR(i, &master);
					}
					else {
						/* we got some data from a client*/
						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()");
								}
							}
						}
					}
				}
			}
		}
	}

	return 0;
}