[c/C++] socket programming tutorial with example

Source:
https://www.tutorialspoint.com/unix_sockets/socket_server_example.htm
https://www.tutorialspoint.com/unix_sockets/socket_client_example.htm

Part 1: source code:
server.c:

#include <stdio.h>
#include <stdlib.h>

#include <netdb.h>
#include <netinet/in.h>

#include <string.h>

int main( int argc, char *argv[] ) {
   int sockfd, newsockfd, portno, clilen;
   char buffer[256];
   struct sockaddr_in serv_addr, cli_addr;
   int  n;
   
   /* First call to socket() function */
   sockfd = socket(AF_INET, SOCK_STREAM, 0);
   
   if (sockfd < 0) {
      perror("ERROR opening socket");
      exit(1);
   }
   
   /* Initialize socket structure */
   bzero((char *) &serv_addr, sizeof(serv_addr));
   portno = 5001;
   
   serv_addr.sin_family = AF_INET;
   serv_addr.sin_addr.s_addr = INADDR_ANY;
   serv_addr.sin_port = htons(portno);
   
   /* Now bind the host address using bind() call.*/
   if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
      perror("ERROR on binding");
      exit(1);
   }
      
   /* Now start listening for the clients, here process will
      * go in sleep mode and will wait for the incoming connection
   */
   
   listen(sockfd,5);
   clilen = sizeof(cli_addr);
   
   /* Accept actual connection from the client */
   newsockfd = accept(sockfd, (struct sockaddr *)&cli_addr, &clilen);
 
   if (newsockfd < 0) {
      perror("ERROR on accept");
      exit(1);
   }
   
   /* If connection is established then start communicating */
   bzero(buffer,256);
   n = read( newsockfd,buffer,255 );
   
   if (n < 0) {
      perror("ERROR reading from socket");
      exit(1);
   }
   
   printf("Here is the message: %s\n",buffer);
   
   /* Write a response to the client */
   n = write(newsockfd,"I got your message",18);
   
   if (n < 0) {
      perror("ERROR writing to socket");
      exit(1);
   }
      
   return 0;
}

client.c:

#include <stdio.h>
#include <stdlib.h>

#include <netdb.h>
#include <netinet/in.h>

#include <string.h>

int main(int argc, char *argv[]) {
   int sockfd, portno, n;
   struct sockaddr_in serv_addr;
   struct hostent *server;
   
   char buffer[256];
   
   if (argc < 3) {
      fprintf(stderr,"usage %s hostname port\n", argv[0]);
      exit(0);
   }
 
   portno = atoi(argv[2]);
   
   /* Create a socket point */
   sockfd = socket(AF_INET, SOCK_STREAM, 0);
   
   if (sockfd < 0) {
      perror("ERROR opening socket");
      exit(1);
   }
 
   server = gethostbyname(argv[1]);
   
   if (server == NULL) {
      fprintf(stderr,"ERROR, no such host\n");
      exit(0);
   }
   
   bzero((char *) &serv_addr, sizeof(serv_addr));
   serv_addr.sin_family = AF_INET;
   bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length);
   serv_addr.sin_port = htons(portno);
   
   /* Now connect to the server */
   if (connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {
      perror("ERROR connecting");
      exit(1);
   }
   
   /* Now ask for a message from the user, this message
      * will be read by server
   */
 
   printf("Please enter the message: ");
   bzero(buffer,256);
   fgets(buffer,255,stdin);
   
   /* Send message to the server */
   n = write(sockfd, buffer, strlen(buffer));
   
   if (n < 0) {
      perror("ERROR writing to socket");
      exit(1);
   }
   
   /* Now read server response */
   bzero(buffer,256);
   n = read(sockfd, buffer, 255);
   
   if (n < 0) {
      perror("ERROR reading from socket");
      exit(1);
   }
 
   printf("%s\n",buffer);
   return 0;
}

Part 2: compile:
gcc server.c -o server
gcc client.c  -o client


Part 3:    execution:

Step 1: execute server command
./server

Step 2: execute client command
./client 127.0.0.1 5001
Please enter the message: hello world
I got your message

Step 3: check the result on server
Here is the message: hello world