server.c

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


void error(const char *msg)
{
    perror(msg);
    exit(1);
}

int main(int argc, char *argv[])
{
    if(argc < 2){
        fprintf(stderr,"PORT no. not provided!!\n");
        exit(1);
    }
    int sockfd, newsockfd, portno, n;
    char buffer[255];

    struct sockaddr_in serv_addr, cli_addr;
    socklen_t clilen;

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    if(sockfd <0){
        error("Error opening a socket!!");
    }
    bzero((char *) &serv_addr, sizeof(serv_addr));
    portno = atoi(argv[1]);
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(portno);

    if(bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr))<0)
    {
        error("Binding Failed!!");
    }

    listen(sockfd, 5 );
    clilen = sizeof(cli_addr);

    newsockfd = accept(sockfd , (struct sockaddr *) &cli_addr, &clilen);
    if(newsockfd < 0)
    error("Error on Accept");

    while(1){
        bzero(buffer, 255);
        n= read(newsockfd , buffer, 255);
        if(n<0)
            error("Error on reading.");
        printf("Client : %s\n", buffer);
        bzero(buffer , 255);
        fgets(buffer, 255, stdin);

        n= write(newsockfd, buffer, strlen(buffer));
        if(n < 0)
            error("Error on writing");

        int i = strncmp("bye" , buffer,3);
        if( i == 0){
            break;
        }

    }
    close(newsockfd);
    close(sockfd);
return 0;
}