在c中一次处理多个连接

Question

I am able to create a socket , binding it to connection , listening on it and receiving results but in all this i have just 1 connection .How do i handle multiple incoming connection in c?I went through the net got some stuff but couldn't get it working..

Please help.

Answer 1

you can use fork / threads / some poll or framework functions.

simple fork example from google:

#include <stdio.h>
#include <strings.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <stdlib.h>

void doprocessing (int sock)
{
    int n;
    char buffer[256];

    bzero(buffer,256);

    n = read(sock,buffer,255);
    if (n < 0)
    {
        perror("ERROR reading from socket");
        exit(1);
    }
    printf("Here is the message: %s\n",buffer);
    n = write(sock,"I got your message",18);
    if (n < 0)
    {
        perror("ERROR writing to socket");
        exit(1);
    }
}

int main( int argc, char *argv[] )
{
    int sockfd, newsockfd, portno;
    socklen_t clilen;
    struct sockaddr_in serv_addr, cli_addr;

    /* First call to socket() function */
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0)
    {
        perror("ERROR opening socket");
        exit(1);
    }
    /* Initialize socket structure */
    bzero((char *) &serv_addr, sizeof(serv_addr));
    portno = 5001;
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(portno);

    /* Now bind the host address using bind() call.*/
    if (bind(sockfd, (struct sockaddr *) &serv_addr,
                          sizeof(serv_addr)) < 0)
    {
         perror("ERROR on binding");
         exit(1);
    }
    /* Now start listening for the clients, here
     * process will go in sleep mode and will wait
     * for the incoming connection
     */
    listen(sockfd,5);
    clilen = sizeof(cli_addr);
    while (1)
    {
        newsockfd = accept(sockfd,
                (struct sockaddr *) &cli_addr, &clilen);
        if (newsockfd < 0)
        {
            perror("ERROR on accept");
            exit(1);
        }
        /* Create child process */
        pid_t pid = fork();
        if (pid < 0)
        {
            perror("ERROR on fork");
            exit(1);
        }
        if (pid == 0)
        {
            /* This is the client process */
            close(sockfd);
            doprocessing(newsockfd);
            exit(0);
        }
        else
        {
            close(newsockfd);
        }
    } /* end of while */
}

Answer 2

I'll can give you a brief description of how that would work.

You need to set up a system that listens for a connection, and when there is one it pushes it into a list of open connections. After it stores the connection in the list you create another listener. Periodically prune your list based on the connection status.

Answer 3

You don't mention which OS, so I'm going to assume Unix/Linux.

The most common method to handle multiple connections is to process each connection in a separate process via fork() or using threads using pthreads for example. The idea is that the server waits for a connection, when one is accepted a new process is created using fork() or a new thread is created to handle the new connection. Here is a decent tutorial you might want to have a look at.

Here is a useful pthreads tutorial