Question

I am needing to initialize a server socket and wait for incoming connections in C programming. I am also required to create a thread to handle my client and able to pass messages between them asynchronously. I would ideally like to start my server with pthreads to allow for multiple connections.

I have 2 functions started:

int serverRun(){

this will be the meat of the server code with sockets

}

int serverStart()

{

This is where I want to initiate the server

}

Answer 1

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<pthread.h>
 
// initialise functions and variables
void *connection_handler(void *);
int socket_desc , client_sock , c;
struct sockaddr_in server , client;
pthread_t thread_id;
     
int serverRun()
{
    listen(socket_desc , 3);

    //Accept and incoming connection
    printf("Waiting for incoming connections...\n");
    c = sizeof(struct sockaddr_in);
     
    //Accept and incoming connection
    printf("Waiting for incoming connections...\n");
    c = sizeof(struct sockaddr_in);
        
    while( (client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c)) )
    {
        printf("Connection accepted\n");
         
        if( pthread_create( &thread_id , NULL ,  connection_handler , (void*) &client_sock) < 0)
        {
            printf("Could not create thread\n");
            return 1;
        }
         
        //Now join the thread , so that we dont terminate before the thread
        //pthread_join( thread_id , NULL);
        printf("Handler assigned\n");
    }
     
    if (client_sock < 0)
    {
        printf("accept failed\n");
        return 1;
    }
}
int serverStart()
{
    //Create server socket
    socket_desc = socket(AF_INET , SOCK_STREAM , 0);
    if (socket_desc == -1)
    {
        printf("Could not create socket\n");
        return 0;
    }
    printf("Server Socket Created\n");
     
    //Prepare the sockaddr_in structure
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(8000); // You can use any port here
     
    //Bind the port to the server socket to be active listner
    if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
    {
        printf("bind failed\n");
        return 0;
    }
    printf("bind done\n");
    return 1;
}
 
int main(int argc , char *argv[])
{
    int serverStatus = serverStart();
    if(serverStatus = 1)
    {
        printf("Server Created\n");
    }
    else
    {
        printf("Server Creation failed\n");
    }
    int a = serverRun();

    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 read_size;
    char *message , client_message[2000];
     
    //Send some messages to the client
    message = "Greetings! I am your connection handler\n";
    write(sock , message , strlen(message));
     
    message = "Now type something and i shall repeat what you type \n";
    write(sock , message , strlen(message));
     
    //Receive a message from client
    while( (read_size = recv(sock , client_message , 2000 , 0)) > 0 )
    {
        //end of string marker
                client_message[read_size] = '\0';
                
                //Send the message back to client
        write(sock , client_message , strlen(client_message));
                
                //clear the message buffer
                memset(client_message, 0, 2000);
    }
     
    if(read_size == 0)
    {
        printf("Client disconnected\n");
        fflush(stdout);
    }
    else if(read_size == -1)
    {
        printf("recv failed\n");
    }
         
    return 0;
} 

Here is the required c c0de for server