multithread server/client implementation in C

Question

I have just started learning basic networking concepts.I am trying to implement a multithread server-client prog in C.but the problem is instead of running multiple windows/

Answer 1

Firstly, if you fork(), you will be creating additional processes, not additional threads. To create additional threads, you want to use pthread_create.

Secondly, as you are a student, the canonical answer here is 'read Stephens'. Not only is this an invaluable tool even for those of us experienced in writing socket I/O routines, but also it contains examples of non-threaded non-forking async I/O, and various ways to add threads and forking to them. I believe the one you want is: http://www.amazon.com/Programming-Environment-Addison-Wesley-Professional-Computing/dp/0321637739 (chapter 14 if memory serves). This should be in your college library.

Answer 2

You can create multiple clients using thread. Create a separate thread for each client and then from thread handler connect to the server. I am not sure if it is a good way or not.

Code:

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

#define MAX_SIZE 50
#define NUM_CLIENT 5
void *connection_handler(void *socket_desc);
int main()
{
    int socket_desc , new_socket , c , *new_sock, i;
    pthread_t sniffer_thread;
    for (i=1; i<=NUM_CLIENT; i++) {
        if( pthread_create( &sniffer_thread , NULL ,  connection_handler , (void*) i) < 0)
        {
            perror("could not create thread");
            return 1;
        }
        sleep(3);
    }
    pthread_exit(NULL);
    return 0;
}

void *connection_handler(void *threadid)
{
    int threadnum = (int)threadid;
    int sock_desc;
    struct sockaddr_in serv_addr;
    char sbuff[MAX_SIZE],rbuff[MAX_SIZE];

    if((sock_desc = socket(AF_INET, SOCK_STREAM, 0)) < 0)
        printf("Failed creating socket\n");

    bzero((char *) &serv_addr, sizeof (serv_addr));

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serv_addr.sin_port = htons(8888);

    if (connect(sock_desc, (struct sockaddr *) &serv_addr, sizeof (serv_addr)) < 0) {
        printf("Failed to connect to server\n");
    }

    printf("Connected successfully client:%d\n", threadnum);
    while(1)
    {
        printf("For thread : %d\n", threadnum);
        fgets(sbuff, MAX_SIZE , stdin);
        send(sock_desc,sbuff,strlen(sbuff),0);

        if(recv(sock_desc,rbuff,MAX_SIZE,0)==0)
            printf("Error");
        else
           fputs(rbuff,stdout);

        bzero(rbuff,MAX_SIZE);
        sleep(2);
    }
    close(sock_desc);
    return 0;
}

For understanding purpose, i used sleep.

REF:

http://www.amazon.com/UNIX-Network-Programming-Richard-Stevens/dp/0139498761

http://beej.us/guide/bgnet/

https://computing.llnl.gov/tutorials/pthreads/