Question

Write and run an algorithm for a TCP client and a TCP server with the

following specifications:

(i) The server should be able to handle at least 5 clients concurrently

(ii) A client program sends a string to a server.

(iii) The server program converts lower case latters to upper case

letters and vice versa.

(iv) The converted string is returned to the client.

(v) The client program prints the result.

Answer 1

TCP Server:

#include <stdio.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#define MAX 80
#define PORT 8080
#define SA struct sockaddr
   
// Function designed for chat between client and server.
void func(int sockfd)
{
    char buff[MAX];
    int n;
    // infinite loop for chat
    for (;;) {
        bzero(buff, MAX);
   
        // read the message from client and copy it in buffer
        read(sockfd, buff, sizeof(buff));
        // print buffer which contains the client contents
        printf("From client: %s\t To client : ", buff);
        bzero(buff, MAX);
        n = 0;
        // copy server message in the buffer
        while ((buff[n++] = getchar()) != '\n')
            ;
   
        // and send that buffer to client
        write(sockfd, buff, sizeof(buff));
   
        // if msg contains "Exit" then server exit and chat ended.
        if (strncmp("exit", buff, 4) == 0) {
            printf("Server Exit...\n");
            break;
        }
    }
}
   
// Driver function
int main()
{
    int sockfd, connfd, len;
    struct sockaddr_in servaddr, cli;
   
    // socket create and verification
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        printf("socket creation failed...\n");
        exit(0);
    }
    else
        printf("Socket successfully created..\n");
    bzero(&servaddr, sizeof(servaddr));
   
    // assign IP, PORT
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(PORT);
   
    // Binding newly created socket to given IP and verification
    if ((bind(sockfd, (SA*)&servaddr, sizeof(servaddr))) != 0) {
        printf("socket bind failed...\n");
        exit(0);
    }
    else
        printf("Socket successfully binded..\n");
   
    // Now server is ready to listen and verification
    if ((listen(sockfd, 5)) != 0) {
        printf("Listen failed...\n");
        exit(0);
    }
    else
        printf("Server listening..\n");
    len = sizeof(cli);
   
    // Accept the data packet from client and verification
    connfd = accept(sockfd, (SA*)&cli, &len);
    if (connfd < 0) {
        printf("server accept failed...\n");
        exit(0);
    }
    else
        printf("server accept the client...\n");
   
    // Function for chatting between client and server
    func(connfd);
   
    // After chatting close the socket
    close(sockfd);
}

TCP Client:

#include <netdb.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/socket.h>

#define MAX 80

#define PORT 8080

#define SA struct sockaddr

void func(int sockfd)

{

    char buff[MAX];

    int n;

    for (;;) {

        bzero(buff, sizeof(buff));

        printf("Enter the string : ");

        n = 0;

        while ((buff[n++] = getchar()) != '\n')

            ;

        write(sockfd, buff, sizeof(buff));

        bzero(buff, sizeof(buff));

        read(sockfd, buff, sizeof(buff));

        printf("From Server : %s", buff);

        if ((strncmp(buff, "exit", 4)) == 0) {

            printf("Client Exit...\n");

            break;

        }

    }

}

   

int main()

{

    int sockfd, connfd;

    struct sockaddr_in servaddr, cli;

   

    // socket create and varification

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    if (sockfd == -1) {

        printf("socket creation failed...\n");

        exit(0);

    }

    else

        printf("Socket successfully created..\n");

    bzero(&servaddr, sizeof(servaddr));

   

    // assign IP, PORT

    servaddr.sin_family = AF_INET;

    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");

    servaddr.sin_port = htons(PORT);

   

    // connect the client socket to server socket

    if (connect(sockfd, (SA*)&servaddr, sizeof(servaddr)) != 0) {

        printf("connection with the server failed...\n");

        exit(0);

    }

    else

        printf("connected to the server..\n");

   

    // function for chat

    func(sockfd);

   

    // close the socket

    close(sockfd);

}