Socket vježba (primjer server-side koda)

server.c

/*
 ** server.c -- a stream socket server demo
 */
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <errno.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <sys/wait.h>
 #include <signal.h>
 #define MYPORT 3490 // Port koji se koristi za konekciju
 #define BACKLOG 10 // 10 mogućih konekcija

void sigchld_handler(int s) {
	while(wait(NULL) > 0);
}

int main(void) {
	int sockfd, new_fd; // listen on sock_fd, new connection on new_fd
	struct sockaddr_in my_addr; // my address information
	struct sockaddr_in their_addr; // connector's address information
	int sin_size;
	struct sigaction sa;
	int yes=1;
	if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}
	if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) {
		perror("setsockopt");
		exit(1);
	}

	my_addr.sin_family = AF_INET; // host byte order
	my_addr.sin_port = htons(MYPORT); // short, network byte order
	my_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP
	memset(&(my_addr.sin_zero), '\0', 8); // zero the rest of the struct
 	if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
		perror("bind");
		exit(1);
	}
	if (listen(sockfd, BACKLOG) == -1) {
		perror("listen");
		exit(1);
 	}
	sa.sa_handler = sigchld_handler; // reap all dead processes
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGCHLD, &sa, NULL) == -1) {
 		perror("sigaction");
 		exit(1);
 	}
 	while(1) { // main accept() loop
 		sin_size = sizeof(struct sockaddr_in);
 		if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) == -1) {
 			perror("accept");
 			continue;
 		}
 		printf("server: got connection from %s\n",
 		inet_ntoa(their_addr.sin_addr));
 		if (!fork()) { // this is the child process
 			close(sockfd); // child doesn't need the listener
 			if (send(new_fd, "Hello, world!\n", 14, 0) == -1)
 				perror("send");
 			close(new_fd);
 			exit(0);
 		}
 		close(new_fd); // parent doesn't need this
 	}
 	return 0;
 }