Write two programs in C: hello_client and hello_server a. The server listens for, and accepts, a single TCP connection; it reads all the data it can from that connection, and prints it to the screen; then it closes the connection

// TCP Server

#include <unistd.h>

#include <stdio.h>

#include <sys/socket.h>

#include <stdlib.h>

#include <netinet/in.h>

#include <string.h>

#define PORT 8080

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

{

    int server_fd, new_socket, valread;

    struct sockaddr_in address;

    int opt = 1;

    int addrlen = sizeof(address);

    char buffer[1024] = {0};

    char *hello = "Hello from server";  

    // Creating socket file descriptor

    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0)

    {  perror("socket failed");

       exit(EXIT_FAILURE);

    }

      

    // Forcefully attaching socket to the port 8080

    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT,&opt, sizeof(opt)))

    {   perror("setsockopt");

        exit(EXIT_FAILURE);

    }

    address.sin_family = AF_INET;

    address.sin_addr.s_addr = INADDR_ANY;

    address.sin_port = htons( PORT );

      

    // Forcefully attaching socket to the port 8080

    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address))<0)

    {

        perror("bind failed");

        exit(EXIT_FAILURE);

    }

    if (listen(server_fd, 3) < 0)

    {

        perror("listen");

        exit(EXIT_FAILURE);

    }

    if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0)

    { perror("accept");

        exit(EXIT_FAILURE);

    }

    valread = read( new_socket , buffer, 1024);

    printf("%s\n",buffer );

    send(new_socket , hello , strlen(hello) , 0 );

    printf("Hello message sent\n");

    return 0;

}

// Tcp Client  

#include <stdio.h>

#include <sys/socket.h>

#include <stdlib.h>

#include <netinet/in.h>

#include <string.h>

#define PORT 8080

  

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

{

    struct sockaddr_in address;

    int sock = 0, valread;

    struct sockaddr_in serv_addr;

    char *hello = "Hello from client";

    char buffer[1024] = {0};

    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0)

    {

        printf("\n Socket creation error \n");

        return -1;

    }

  

    memset(&serv_addr, '0', sizeof(serv_addr));

  

    serv_addr.sin_family = AF_INET;

    serv_addr.sin_port = htons(PORT);

      

    // Convert IPv4 and IPv6 addresses from text to binary form

    if(inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr)<=0) 

    {

        printf("\nInvalid address/ Address not supported \n");

        return -1;

    }

  

    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)

    {

        printf("\nConnection Failed \n");

        return -1;

    }

    send(sock , hello , strlen(hello) , 0 );

    printf("Hello message sent\n");

    valread = read( sock , buffer, 1024);

    printf("%s\n",buffer );

    return 0;

}

Steps to compile and Run

Open one Terminal in Linux and compile and run TCP server program    

1. Compile the server program

gcc tcpserver.c -o tcpser)

2. Run server using

./tcpser

Output 

[root@localhost TCP]# gcc tcpserver.c -o tcpser

[root@localhost TCP]# ./tcpser

Client : Hello from client

Hello message sent.

Open one Terminal in Linux and compile and run TCP client program    

1.       compile tcp client program

gcc tcpclient.c -o tcpcli)

2.       Run tcp client

./tcpcli)

Output 

[root@localhost TCP# gcc tcpclient.c -o tcpcli

[root@localhost TCP]# ./tcpcli

Hello message sent.