rttserver.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

// importing libraries  
int main(){
//intializations
  char *ip = "127.0.0.1";
  int port = 5565;

  int server_sock, client_sock;
  struct sockaddr_in server_addr, client_addr;
  socklen_t addr_size;
  char buffer[100];
  int n;
//for TCP its STREAM for UDP USE DGRAM.
  server_sock = socket(AF_INET, SOCK_STREAM, 0);
  if (server_sock < 0){
    perror("[-]Socket error");
    exit(1);
  }
  printf("[+]TCP server socket created.\n");

  memset(&server_addr, '\0', sizeof(server_addr));
  server_addr.sin_family = AF_INET;
  server_addr.sin_port = port;
  server_addr.sin_addr.s_addr = inet_addr(ip);

  n = bind(server_sock, (struct sockaddr*)&server_addr, sizeof(server_addr));
  if (n < 0){
    perror("[-]Bind error");
    exit(1);
  }
  printf("[+]Bind to the port number: %d\n", port);

  listen(server_sock, 5);
  printf("Listening...\n");
	// initially buffer 100 bytes change it according to need of packet sizes
bzero(buffer, 100);
int i=1;
addr_size = sizeof(client_addr);
    client_sock = accept(server_sock, (struct sockaddr*)&client_addr, &addr_size);
    printf("[+]Client connected.\n");
    
  // two times receiveing and sending packets to measure RTT
  while(i<=2){
    
    recv(client_sock, buffer, sizeof(buffer), 0);
    printf("Client: %s\n", buffer);
	
  long int presize = sizeof(buffer);
  bzero(buffer,100);
      char string[20];
  sprintf(string, "%d", i);   
    strcpy(buffer,string );
    send(client_sock, buffer, strlen(buffer), 0);
    ++i;
   
    bzero(buffer, presize);
  }
 close(client_sock);
    printf("[+]Client disconnected.\n\n");

  return 0;
}