Question

334423. #1: Write a program that optionally accepts an address and a port from the command line. If there is no address/port on the command line, it should create a TCP socket and print the address (i.e. server mode). If there is an address/port, it should connect to it (i.e. client mode). Once the connections are set up, each side should enter a loop of receive, print what it received, then send a message. The message should be “ping” from the client and “pong” from the server.

Hints:

You will need to pick a port for the server – something over 1024.

Ensure that you open your firewall to let the signal through.

Answer 1

Herewith I am providing a C program to demonstrate the given client-server environment.

server.c

#include<stdio.h>
//This header file contains declarations used in most input and output and is typically included in all C programs.

#include<stdlib.h>
#include<string.h>
#include<unistd.h>

#include<sys/socket.h>
// The header file socket.h includes a number of definitions of structures needed for sockets.

#include<netinet/in.h>
//The header file in.h contains constants and structures needed for internet domain addresses

#include<sys/types.h>
//This header file contains definitions of a number of data types used in system calls. These types are used in the next two include files.

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

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

if(argc<2)
{error("\nPort number not provided, program terminated\n");}

int sock, newsock, n, port, i;
char buffer[200];
struct sockaddr_in address;
socklen_t len;
len = sizeof(address);
bzero((char *)&address, sizeof(address));

if((sock = socket(AF_INET, SOCK_STREAM, 0))==0)
error("\nERROR: Socket not created\n");

port = atoi(argv[1]);
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons(port);

bind(sock, (struct sockaddr*)&address, sizeof(address));

listen(sock, 3);

newsock = accept(sock, (struct sockaddr *)&address, &len);
if(newsock<0)
error("ERROR: Accept");

/*
bzero(buffer, 200);
n = read(newsock, buffer, 200);
if(n<0)
error("ERROR: READING");
printf("\nClient: %s", buffer);
*/
do{
   bzero(buffer, 200);
   n = read(newsock, buffer, 200);
   if(n<0)
       error("ERROR: READING");
   printf("\nClient: %s", buffer);

   bzero(buffer, 200);
   fgets(buffer, 200, stdin);
   n = write(newsock, buffer, strlen(buffer));
   if(n<0)
       error("ERROR: WRITING");
   printf("\nMe: %s",buffer);
   i = strncmp(buffer,"Bye", 3);
   if(i==0)
   break;
}while(1);

close(newsock);
close(sock);

return 0;
}

client.c

#include<stdio.h>
//This header file contains declarations used in most input and output and is typically included in all C programs.

#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<netdb.h>

#include<sys/socket.h>
// The header file socket.h includes a number of definitions of structures needed for sockets.

#include<netinet/in.h>
//The header file in.h contains constants and structures needed for internet domain addresses

#include<sys/types.h>
// This header file contains definitions of a number of data types used in system calls. These types are used in the next two include files.

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

int main(int argc, char * argv[])
{
if(argc<2)
error("\nIP address, Port number not provided\n");

if(argc<3)
error("\nPort number not provided\n");

int sock, n, port, i;
struct sockaddr_in server;
struct hostent *address;
char buffer[200];
socklen_t len;
len = sizeof(server);
bzero((char *)&server, sizeof(server));

sock = socket(AF_INET, SOCK_STREAM, 0);
//int socket(domain, type, protocol)

if(sock<0)
   error("Socket Could Not Be Created\n");
else
   printf("Socket Created Succesfully\n");

port = atoi(argv[2]);
server.sin_family = AF_INET;
server.sin_port = htons(port);

address = gethostbyname(argv[1]);
bcopy((char *)address->h_addr, (char*)&server.sin_addr.s_addr, address->h_length);

//inet_pton(&server, , &server.s_addr);

n = connect(sock, (struct sockaddr*)&server, len);
if(n<0)
error("ERROR: Connect");

do{
   bzero(buffer, 200);
   fgets(buffer, 200, stdin);
   n = write(sock, buffer, strlen(buffer));
   if(n<0)
       error("ERROR: WRITING");
   printf("\nMe: %s", buffer);

   bzero(buffer, 200);
   n = read(sock, buffer, 200);
   if(n<0)
       error("ERROR: READING");
   printf("\nServer: %s", buffer);
   i = strncmp(buffer,"Bye", 3);
   if(i==0)
       break;
}while(1);

close(sock);
return 0;
}

Output screenshot