TCP server

server.c

/* -*- compile-command: "gcc -Wall -pedantic -g3 server.c -o server" -*- */

/**
   TCP server implementation

   1. Create a TCP socket.
   2. bind(),   Bind the socket to server address.
   3. listen(), Put the server socket in a passive mode, it waits for the client to make a connection
   4. accept(), Connection is established between client and server, ready to transfer data.
   5. go back to Step 3.
**/


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>

#define SIZE_BUFF 1000
#define PORT 8080

// Function designed for chat between client and server.
void func_server(int sockfd)
{
    char buff[SIZE_BUFF];
    int nread = 0, nwrite = 0;

    // infinite loop
    for (;;) {

        memset(buff, 0, sizeof(buff));

        errno = 0;
	// read the message from client and copy it in buffer
	nread = read(sockfd, buff, sizeof(buff));
        if(nread == -1) {
            perror("read");
            exit(EXIT_FAILURE);
        }
	// print buffer which contains the client contents
	printf("\nMessage From client: %s\n", buff);
        printf("Bytes read = %ld\n", strlen(buff));

        memset(buff, 0, sizeof(buff));

        printf("Message from client received --> sending ACK...\n");

        errno = 0;
	// and send that buffer to client
	nwrite = write(sockfd, "ACK -- Message received", sizeof(buff));
        if (nwrite == -1) {
            perror("write");
            exit(EXIT_FAILURE);
        }
    }
}

// MAIN
int main()
{
    struct sockaddr_in servaddr, cli;
    int sockfd, connfd;
    unsigned int client_len;

    errno = 0;
    // Socket create and verification
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd == -1) {
	printf("Socket creation failed...\n");
        perror("Socket");
	exit(EXIT_FAILURE);
    } else {
	printf("Socket successfully created..\n");
    }

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

    // Assign IP, PORT
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(PORT);

    errno = 0;
    // Binding newly created socket to given IP and verification
    if ((bind(sockfd, (struct sockaddr*) &servaddr, sizeof(servaddr))) != 0) {
	printf("Socket bind() failed...\n");
        perror("Bind");
	exit(EXIT_FAILURE);
    } else {
	printf("Socket successfully binded...\n");
    }

    errno = 0;
    // Now server is ready to listen and verification
    if((listen(sockfd, 5)) != 0) {
	printf("Server listen() failed...\n");
        perror("Listen");
        exit(EXIT_FAILURE);
    } else {
	printf("Server listening...\n");
    }

    client_len = sizeof(struct sockaddr_in);

    errno = 0;
    // Accept the data packet from client
    connfd = accept(sockfd, (struct sockaddr*) &cli, (socklen_t*) &client_len);
    if (connfd < 0) {
	printf("Server acccept() failed...\n");
        perror("Accept");
        exit(0);
    } else {
	printf("Server acccept the client...\n");
    }
    
    // Function for SERVER
    func_server(connfd);

    // Close the socket
    close(sockfd);

    return 0;
}