Simple c program that listens to some port and prints "Hello World" as responce

helloREST.c

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

/*
 Test application for k8s servies
 Server that responds with HTTP result on specified port
 Build: gcc -ohelloREST hello-listen.c 
 Run: ./helloREST 8001
 Test by running: curl localhost:8001

 Ted Wennmark 2019
*/

const char *reply = 
      "HTTP/1.1 200 OK\n"
      "Content-Type: text/html\n"
      "Content-Length: 12\n"
      "Accept-Ranges: bytes\n"
      "Connection: close\n"
      "\n"
      "Hello World!\n";

int print_usage(char * name)
{
   fprintf(stderr,"ERROR: %s <port>\n", name);
}

void error(char *msg)
{
   perror(msg);
   exit(1);
}

void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET)
        return &(((struct sockaddr_in*)sa)->sin_addr);
    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(int argc, char *argv[])
{
   int port, my_sock, cli_sock, size;
   struct sockaddr_in addr;
   char s[INET6_ADDRSTRLEN];

   if (argc != 2)
   {
      print_usage(argv[0]);
      exit(1);
   }
   port=atoi(argv[1]);

   my_sock = socket(PF_INET, SOCK_STREAM, 0);

   memset(&addr,0,sizeof(addr));
   addr.sin_family = AF_INET;
   addr.sin_port = htons(port);
   addr.sin_addr.s_addr = INADDR_ANY;

   if(bind(my_sock, (struct sockaddr *) &addr, sizeof(addr))!=0)
   {
      error("ERROR on bind()\n");
   }

   if (listen(my_sock, 16)!=0)
   {
      error("ERROR on listen()\n");
   }

   size = sizeof(addr);
   while ((cli_sock=accept(my_sock, (struct sockaddr *) &addr, &size)) > 0)
   {
       inet_ntop(addr.sin_family,
                get_in_addr((struct sockaddr *)&addr),
                s, sizeof s);
       printf("Server: got connection from %s\n", s);
       send(cli_sock, reply, strlen(reply), 0);
       close(cli_sock);
   }

   return 0; 
}