Socket programming in C using Threads

/*

    C socket server example, handles multiple clients using threads

    Compile

    gcc server.c -lpthread -o server

*/

 

#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;
    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 = inet_addr("127.0.0.1");
    server.sin_port = htons( 8888 );

    //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);

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

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

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

        //Now join the thread , so that we dont terminate before the thread
        //pthread_join( thread_id , NULL);
        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 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)
    {
        puts("Client disconnected");
        fflush(stdout);
    }
    else if(read_size == -1)
    {
        perror("recv failed");
    }
    return 0;
} 


/*

    C socket client example, handles multiple clients using threads
    Compile
    gcc -o client client.c
    run using -->  ./client 

*/

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

void error(char *msg)
{
    perror(msg);
    exit(0);
}

int main(int argc, char *argv[])
{
    int sockfd, portno, n,p,count=0;
    struct sockaddr_in serv_addr;
    char buff[256],client[100],temp_buff[100];
    FILE *id;
    id = popen("id -n -u","r");
    fgets(client,100,id);
    strtok(client,"\n");
    portno = 8888;

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

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0)
        error("ERROR opening socket"); 
    bzero((char *) &serv_addr, sizeof(serv_addr));

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

    //getnameinfo((struct sockaddr *)&serv_addr, sizeof serv_addr, host, sizeof host, service, sizeof service, 0);
    if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0)
    error("ERROR connecting");
    while(1)
    {
      if (count == 0)
      {
        p = write(sockfd,client,strlen(client));
        if (p < 0)
            error("ERROR writing to socket");
        bzero(temp_buff,sizeof(temp_buff));
        n = read(sockfd,temp_buff,99);
        if (n < 0)
            error("ERROR reading from socket");
        count++;
      }
      else
      {
        printf("%s: ",client);
        bzero(buff,256);
        fgets(buff,255,stdin);
        n = write(sockfd,buff,strlen(buff));
        if (n < 0)
            error("ERROR writing to socket");
        if (buff[0] == 'q')
        {
            close(sockfd);
            break;
        }

        n = read(sockfd,buff,255);
        if (n < 0)
            error("ERROR reading from socket");
        printf("%s:%s",temp_buff,buff);
    }
       }    
    return 0;
}