Socket

http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html

Internet programming

мрежов сървър чака връзка на порт 3914

/***************************************************************\
 * 
 * server.c -- Hello world! socket connection
 * 
 * 
 * source: http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html
 * 
 * edited by: ilianko
\***************************************************************/

#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 <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h> // child process
#include <signal.h>

#define PORT "3491"  // the port users will be connecting to

#define BACKLOG 10     // how many pending connections queue will hold
#define MAXDATASIZE 100

void sigchld_handler(int s)
{
    while(waitpid(-1, NULL, WNOHANG) > 0);
}


// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) 
    {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void)
{
    int sockfd, new_fd;  // listen on sock_fd, new connection on new_fd
    
    struct addrinfo hints, *servinfo, *p;
    
    struct sockaddr_storage their_addr; // connector's address information
    
    socklen_t sin_size;
    
    struct sigaction sa;
    
    int yes=1;
    char s[INET6_ADDRSTRLEN];
    int rv, numbytes;  
    char buf[MAXDATASIZE];
    
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE; // use my IP

    
    if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) 
    {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // loop through all the results and bind to the first we can
    for(p = servinfo; p != NULL; p = p->ai_next) 
    {
        if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1)
        {
            perror("server: socket");
            continue;
        }

        if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1)
        {
            perror("setsockopt");
            exit(1);
        }

        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1)
        {
            close(sockfd);
            perror("server: bind");
            continue;
        }

        break;
    }

    if (p == NULL)  
    {
        fprintf(stderr, "server: failed to bind\n");
        return 2;
    }

    freeaddrinfo(servinfo); // all done with this structure

    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);
    }

    printf("server: waiting for connections...\n");

    while(1) // main accept() loop 
    {  
        sin_size = sizeof their_addr;
        
        //file descriptor of the new connection
        new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
        
        if (new_fd == -1)
        {
            perror("accept");
            continue;
        }

        //convert IP address from network form to printable (x.x.x.x) form
        inet_ntop(their_addr.ss_family,
            get_in_addr((struct sockaddr *)&their_addr),
            s, sizeof s);
        printf("server: got connection from %s\n", s);


        
        if (!fork()) // this is the child process
        { 
            close(sockfd); // child doesn't need the listener
            
            if (!fork())
            {
				scanf("%s", buf);
				while(1)
				{
		          		
				  if (send(new_fd, buf, strlen(buf), 0) == -1)
                perror("send");
                scanf("%s", buf);
			    }
            
            }
            
            if (!fork())
            {    
              while(1)
              {  
				  if ((numbytes = recv(new_fd, buf, MAXDATASIZE-1, 0)) == -1)
                  {
                     perror("recv");
                     exit(1);
                  }
			      buf[numbytes] = '\0';
			      printf("%s\n",buf);
			   }
            }
            
            close(new_fd);
            exit(0);
        }
        close(new_fd);  // parent doesn't need this
    }

    return 0;
}