Question

Using C as the programming language,

Write a concurrent connection-oriented server that can do something simple for connected clients. It should be able to carry out such processing for the client as many times as the client wants until the client indicates it wishes to end the session.

The server should support multiple clients (use telnet as the client in this task). Compile and run the server program.

Try and connect to it from multiple other hosts using telnet as the client program. Use netstat and ps to examine what is going on from separate observation windows on the hosts involved.

Use a distinct and visible message termination character in the server. The ampersand (&) would be fine. Also, the server should use just one buffer for reading.

Thank you... :)

Answer 1

Solution Using C programing Language

ServerSide Code

/**** iserver.c ****/

#include <stdio.h>

#include <stdlib.h>

#include <sys/socket.h>

#include <netinet/in.h>

#define SERVER_PORT 12345

/* Run with a number of incoming connection as argument */

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

{

int i, len, num, rc;

int listen_sd, accept_sd;

/* Buffer for data */

char buffer[100];

struct sockaddr_in addr;

/* If an argument was specified, use it to */

/* control the number of incoming connections */

if(argc >= 2)

num = atoi(argv[1]);

/* Prompt some message */

else

{

printf("Usage: %s <The_number_of_client_connection else 1 will be used>\n", argv[0]);

num = 1;

}

/* Create an AF_INET stream socket to receive */

/* incoming connections on */

listen_sd = socket(AF_INET, SOCK_STREAM, 0);

if(listen_sd < 0)

{

perror("Iserver - socket() error");

exit(-1);

}

else

printf("Iserver - socket() is OK\n");

printf("Binding the socket...\n");

/* Bind the socket */

memset(&addr, 0, sizeof(addr));

addr.sin_family = AF_INET;

addr.sin_addr.s_addr = htonl(INADDR_ANY);

addr.sin_port = htons(SERVER_PORT);

rc = bind(listen_sd, (struct sockaddr *)&addr, sizeof(addr));

if(rc < 0)

{

perror("Iserver - bind() error");

close(listen_sd);

exit(-1);

}

else

printf("Iserver - bind() is OK\n");

/* Set the listen backlog */

rc = listen(listen_sd, 5);

if(rc < 0)

{

perror("Iserver - listen() error");

close(listen_sd);

exit(-1);

}

else

printf("Iserver - listen() is OK\n");

/* Inform the user that the server is ready */

printf("The Iserver is ready!\n");

/* Go through the loop once for each connection */

for(i=0; i < num; i++)

{

/* Wait for an incoming connection */

printf("Iteration: #%d\n", i+1);

printf(" waiting on accept()\n");

accept_sd = accept(listen_sd, NULL, NULL);

if(accept_sd < 0)

{

perror("Iserver - accept() error");

close(listen_sd);

exit(-1);

}

else

printf("accept() is OK and completed successfully!\n");

/* Receive a message from the client */

printf("I am waiting client(s) to send message(s) to me...\n");

rc = recv(accept_sd, buffer, sizeof(buffer), 0);

if(rc <= 0)

{

perror("Iserver - recv() error");

close(listen_sd);

close(accept_sd);

exit(-1);

}

else

printf("The message from client: \"%s\"\n", buffer);

/* Echo the data back to the client */

printf("Echoing it back to client...\n");

len = rc;

rc = send(accept_sd, buffer, len, 0);

if(rc <= 0)

{

perror("Iserver - send() error");

close(listen_sd);

close(accept_sd);

exit(-1);

}

else

printf("Iserver - send() is OK.\n");

/* Close the incoming connection */

close(accept_sd);

}

/* Close the listen socket */

close(listen_sd);

return 0;

}

• Compile and link.

$ gcc -g iserver.c -o iserver

Run the server program. $ ./iserver Usage: ./iserver <The_number_of_client_connection else 1 will be used> Iserver - socket() is OK Binding the socket... Iserver - bind() is OK Iserver - listen() is OK The Iserver is ready! Iteration: #1 waiting on accept()

Client Side Coding:

/****** comclient.c ******/

#include <stdio.h>

#include <stdlib.h>

#include <sys/socket.h>

#include <netinet/in.h>

/* Our server port as in the previous program */

#define SERVER_PORT 12345

main (int argc, char *argv[])

{

int len, rc;

int sockfd;

char send_buf[100];

char recv_buf[100];

struct sockaddr_in addr;

if(argc !=2)

{

printf("Usage: %s <Server_name or Server_IP_address>\n", argv[0]);

exit (-1);

}

/* Create an AF_INET stream socket */

sockfd = socket(AF_INET, SOCK_STREAM, 0);

if(sockfd < 0)

{

perror("client - socket() error");

exit(-1);

}

else

printf("client - socket() is OK.\n");

/* Initialize the socket address structure */

memset(&addr, 0, sizeof(addr));

addr.sin_family = AF_INET;

addr.sin_addr.s_addr = htonl(INADDR_ANY);

addr.sin_port = htons(SERVER_PORT);

/* Connect to the server */

rc = connect(sockfd, (struct sockaddr *)&addr, sizeof(struct sockaddr_in));

if(rc < 0)

{

perror("client - connect() error");

close(sockfd);

exit(-1);

}

else

{

printf("client - connect() is OK.\n");

printf("connect() completed successfully.\n");

printf("Connection with %s using port %d established!\n", argv[1], SERVER_PORT);

}

/* Enter data buffer that is to be sent */

printf("Enter message to be sent to server:\n");

gets(send_buf);

/* Send data buffer to the worker job */

len = send(sockfd, send_buf, strlen(send_buf) + 1, 0);

if(len != strlen(send_buf) + 1)

{

perror("client - send() error");

close(sockfd);

exit(-1);

}

else

printf("client - send() is OK.\n");

printf("%d bytes sent.\n", len);

/* Receive data buffer from the worker job */

len = recv(sockfd, recv_buf, sizeof(recv_buf), 0);

if(len != strlen(send_buf) + 1)

{

perror("client - recv() error");

close(sockfd);

exit(-1);

}

else

{

printf("client - recv() is OK.\n");

printf("The sent message: \"%s\" successfully received by server and echoed back to client!\n", recv_buf);

printf("%d bytes received.\n", len);

}

/* Close the socket */

close(sockfd);

return 0;

}

Compile and link::$ gcc -g comclient.c -o comclient

if you get compilation error change the gets() to the secure version, gets_s(). Run the program and make sure you run the server program as in the previous program example.

$ ./comclient

$ ./comclient bakawali