client side:


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

int authentication(int socket);
int main(int argc, char *argv[])
{

struct sockaddr_in server;
struct hostent *host;
char uname[100];
char buffer[5000];
int portno,socky,n;
int length = 0,ch,i,p;
char cha;
int *new_sock;
int orig_length = 0;

if(argc < 3)
{
perror("insufficient inputs");  //checking the inputs
exit(1);
}

if((socky = socket(AF_INET,SOCK_STREAM,0)) < 0)
{
perror("nerror in socket creation");       //socket creation
exit(1);
}

printf("nsocket successfully created");

server.sin_family = AF_INET;
portno = atoi(argv[2]);
server.sin_port = htons(portno);
host = gethostbyname(argv[1]);
if(host == NULL)
{
perror("nerror in getting host address");
exit(1);
}

memcpy (&server.sin_addr.s_addr, host->h_addr,host->h_length);

if((connect(socky,&server,sizeof(server)))<0)
{
perror("nerror in connection");
exit(1);
}
while(1)
{
printf("n select an option");
printf("n1->student loginn2->Instructor loginn3->Admin loginn");
printf("n came near scanf");
scanf("%d",&ch);
//printf("nselected value: %c",ch)
if(ch == 1)
{


p = authentication(socky);

}
else{
printf("n invalid option");
}

}
return 0;
}





int authentication(int socky)
{
char buffer[5000];
char cha;
char uname[100];
int n,i;
bzero(buffer,5000);
buffer[0] = '1';
buffer[1] = '';
printf("n%s",buffer);
if(n = (write(socky,buffer,strlen(buffer))) < 0)
{
perror("nerror in writing the message");
exit(1);
}
sleep(10);
bzero(buffer,5000);
printf("nenter the username:n");
scanf("%s",&uname);
strcpy(buffer,uname);
printf("%s",buffer);
fgets(buffer,5000,stdin);
if((n = write(socky,buffer,strlen(buffer))) < 0)
{
perror("nerror in writing the message");
exit(1);
}

bzero(buffer,5000);
printf("nenter the password:n");
for(i =0; cha!=10; i++)
{
cha = fgetc(stdin);
//printf("*");
buffer[i] = cha;
}
buffer[i] = '';
printf("n entered password is :%s",buffer);
if((n = write(socky,buffer,strlen(buffer))) < 0)
{
perror("nerror in writing the message");
exit(1);
}
return 0;
}

#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
#include <fcntl.h>
#include <time.h>
//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;
     int n;
     char buffer[5000];

    //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( atoi(argv[1]));

    //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");

      //  if( (n = recv(client_sock,buffer,5000,0)) < 0)
        //      {
          //       perror("nreading from socket failed");
            //     exit(1);
              //}
            //printf("nread message:%s",buffer);

        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  buffer[5000];
   printf("n came inside connection handler");

     while(1)
{
     bzero(buffer,5000);
     if( (n = recv(sock,buffer,5000,0)) < 0)
              {
                 perror("nreading from socket failed");
                 exit(1);
              }
            printf("nread message:%s",buffer);
        if(n < 0)
{
perror("n Reading failed");
}
if(n==0)
      {
        puts("nClient Disconnected");
          break;
      }

sleep(5);
}


     close(sock);
    return 0;
}






output on server side is as follows:
came inside connection handler
read message:1
read message:

read message:mypassword