Multi-threaded echo client server example.

1. Command

 1) Compile:
      gcc -lpthread -o server mserver.c
      gcc -o client mclient.c

  2) Execute
      ./server
      ./client

2. Server

// socket server example, handles multiple clients using threads

#include<stdio.h>
#include<string.h>    //strlen
#include<stdlib.h>    //strlen
#include<sys/socket.h>
#include<arpa/inet.h> //inet_addr
#include<unistd.h>    //write
#include<pthread.h> //for threading , link with lpthread

//the thread function
void *connection_handler(void *);

int main(int argc , char *argv[])
{
    int socket_desc , client_sock , c , *new_sock;
    struct sockaddr_in server , client;

    //Create socket
    socket_desc = socket(AF_INET , SOCK_STREAM , 0);
    if (socket_desc == -1)
    {
        printf("Could not create socket");
    }
    puts("Socket created");

    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons( 3000 );

    //Bind
    if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
    {
        //print the error message
        perror("bind failed. Error");
        return 1;
    }
    puts("bind done");

    //Listen
    listen(socket_desc , 3);

    //Accept and incoming connection
    puts("Waiting for incoming connections...");
    c = sizeof(struct sockaddr_in);

        c=sizeof(struct sockaddr_in);
       while(client_sock=accept(socket_desc,(struct sockaddr*)&client,(socklen_t*)&c))
       {
        puts("Connection accepted");

        pthread_t sniffer_thread;
        new_sock = malloc(1);
        *new_sock = client_sock;

        if( pthread_create( &sniffer_thread , NULL ,  connection_handler , (void*) new_sock) < 0)
        {
            perror("could not create thread");
            return 1;
        }

        puts("Handler assigned");
    }

    if (client_sock < 0)
    {
        perror("accept failed");
        return 1;
    }
    return 0;
}
/*
  This will handle connection for each client
  */
void *connection_handler(void *socket_desc)
{
    //Get the socket descriptor
    int sock = *(int*)socket_desc;
    int n;

        char    sendBuff[100], client_message[2000];

      while((n=recv(sock,client_message,2000,0))>0)
      {

        send(sock,client_message,n,0);
      }
      close(sock);

      if(n==0)
      {
        puts("Client Disconnected");
      }
      else
      {
        perror("recv failed");
      }
    return 0;
}


3. Client

#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

int main()
{
    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(3000);

    if (connect(sock_desc, (struct sockaddr *) &serv_addr, sizeof (serv_addr)) < 0) {
        printf("Failed to connect to server\n");
        return -1;
    }

    printf("Connected successfully - Please enter string\n");
    while(fgets(sbuff, MAX_SIZE , stdin)!=NULL)
    {
      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);//to clean buffer-->IMP otherwise previous word

characters also came
    }
        close(sock_desc);
    return 0;

}


4. Reference
http://stackoverflow.com/questions/21405204/multithread-server-client-implementation-in-c

http://www.mario-konrad.ch/wiki/doku.php?id=programming:multithreading:tutorial-04