Question

1. Write a client program and a server program with multiple clients:

Write a server application with multiple clients. This means your server program must use threads or fork methods to support multiple clients. You will use socket() and connect() system calls in Unix/Linux/Windows to write an application based on client/server socket programming. You can work on this project using either Java or C/C++. Through this assignment you will learn how to design a simple multithreading client-server programming using Java or C/C++.

Answer 1

One Server And Multiple Clients

Using The C Programming For Implementation.........

First Write Server code then Client Code Both of the code are given below...

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Server Program In C

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tcpserver.c

#include"stdio.h"
#include"stdlib.h"
#include"sys/types.h"
#include"sys/socket.h"
#include"string.h"
#include"netinet/in.h"

#define PORT 4444
#define BUF_SIZE 2000
#define CLADDR_LEN 100

void main() {
 struct sockaddr_in addr, cl_addr;
 int sockfd, len, ret, newsockfd;
 char buffer[BUF_SIZE];
 pid_t childpid;
 char clientAddr[CLADDR_LEN];
 
 sockfd = socket(AF_INET, SOCK_STREAM, 0);
 if (sockfd < 0) {
  printf("Error creating socket!\n");
  exit(1);
 }
 printf("Socket created...\n");
 
 memset(&addr, 0, sizeof(addr));
 addr.sin_family = AF_INET;
 addr.sin_addr.s_addr = INADDR_ANY;
 addr.sin_port = PORT;
 
 ret = bind(sockfd, (struct sockaddr *) &addr, sizeof(addr));
 if (ret < 0) {
  printf("Error binding!\n");
  exit(1);
 }
 printf("Binding done...\n");

 printf("Waiting for a connection...\n");
 listen(sockfd, 5);

 for (;;) { //infinite loop
  len = sizeof(cl_addr);
  newsockfd = accept(sockfd, (struct sockaddr *) &cl_addr, &len);
  if (newsockfd < 0) {
   printf("Error accepting connection!\n");
   exit(1);
  }
  printf("Connection accepted...\n");

  inet_ntop(AF_INET, &(cl_addr.sin_addr), clientAddr, CLADDR_LEN);
  if ((childpid = fork()) == 0) { //creating a child process

   close(sockfd); 
//stop listening for new connections by the main process. 
//the child will continue to listen. 
//the main process now handles the connected client.

   for (;;) {
    memset(buffer, 0, BUF_SIZE);
    ret = recvfrom(newsockfd, buffer, BUF_SIZE, 0, (struct sockaddr *) &cl_addr, &len);
    if(ret < 0) {
     printf("Error receiving data!\n");  
     exit(1);
    }
    printf("Received data from %s: %s\n", clientAddr, buffer); 

    ret = sendto(newsockfd, buffer, BUF_SIZE, 0, (struct sockaddr *) &cl_addr, len);   
    if (ret < 0) {  
     printf("Error sending data!\n");  
     exit(1);  
    }  
    printf("Sent data to %s: %s\n", clientAddr, buffer);
   }
  }
  close(newsockfd);
 }
}

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Client Program In C

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tcpclient.c

#include"stdio.h"  
#include"stdlib.h"  
#include"sys/types.h"  
#include"sys/socket.h"  
#include"string.h"  
#include"netinet/in.h"  
#include"netdb.h"
  
#define PORT 4444 
#define BUF_SIZE 2000 
  
int main(int argc, char**argv) {  
 struct sockaddr_in addr, cl_addr;  
 int sockfd, ret;  
 char buffer[BUF_SIZE];  
 struct hostent * server;
 char * serverAddr;

 if (argc < 2) {
  printf("usage: client < ip address >\n");
  exit(1);  
 }

 serverAddr = argv[1]; 
 
 sockfd = socket(AF_INET, SOCK_STREAM, 0);  
 if (sockfd < 0) {  
  printf("Error creating socket!\n");  
  exit(1);  
 }  
 printf("Socket created...\n");   

 memset(&addr, 0, sizeof(addr));  
 addr.sin_family = AF_INET;  
 addr.sin_addr.s_addr = inet_addr(serverAddr);
 addr.sin_port = PORT;     

 ret = connect(sockfd, (struct sockaddr *) &addr, sizeof(addr));  
 if (ret < 0) {  
  printf("Error connecting to the server!\n");  
  exit(1);  
 }  
 printf("Connected to the server...\n");  

 memset(buffer, 0, BUF_SIZE);
 printf("Enter your message(s): ");

 while (fgets(buffer, BUF_SIZE, stdin) != NULL) {
  ret = sendto(sockfd, buffer, BUF_SIZE, 0, (struct sockaddr *) &addr, sizeof(addr));  
  if (ret < 0) {  
   printf("Error sending data!\n\t-%s", buffer);  
  }
  ret = recvfrom(sockfd, buffer, BUF_SIZE, 0, NULL, NULL);  
  if (ret < 0) {  
   printf("Error receiving data!\n");    
  } else {
   printf("Received: ");
   fputs(buffer, stdout);
   printf("\n");
  }  
 }
 
 return 0;    
}  

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How To Execute This Programs

--terminal 1--
gcc tcpserver.c -o server
./server

--terminal 2--
gcc tcpclient.c -o client
./client 192.168.0.4

--terminal 3--
./client 192.168.0.4

• Note that 192.168.0.4 is the IP address of the machine in which the server is running.

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