How to get the IP Address of local computer using C/C++?


In this section we will see how to see the Host name and IP address of the local system in an easier way. We will write a C program to find the host name and IP.

Some of the following functions are used. These functions have different task. Let us see the functions and their tasks.

Sr.NoFunction & Description
1gethostname()
It finds the standard host name for the local computer.
2gethostbyname()
It finds the host information corresponding to a host name from host database
3iten_ntoa()
It converts an IPv4 Internet network address into an ASCII string into dotted decimal format.

Example

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void check_host_name(int hostname) { //This function returns host name for local computer
   if (hostname == -1) {
      perror("gethostname");
      exit(1);
   }
}
void check_host_entry(struct hostent * hostentry) { //find host info from host name
   if (hostentry == NULL){
      perror("gethostbyname");
      exit(1);
   }
}
void IP_formatter(char *IPbuffer) { //convert IP string to dotted decimal format
   if (NULL == IPbuffer) {
      perror("inet_ntoa");
      exit(1);
   }
}
main() {
   char host[256];
   char *IP;
   struct hostent *host_entry;
   int hostname;
   hostname = gethostname(host, sizeof(host)); //find the host name
   check_host_name(hostname);
   host_entry = gethostbyname(host); //find host information
   check_host_entry(host_entry);
   IP = inet_ntoa(*((struct in_addr*) host_entry->h_addr_list[0])); //Convert into IP string
   printf("Current Host Name: %s\n", host);
   printf("Host IP: %s\n", IP);
}

Output

Current Host Name: soumyadeep-VirtualBox
Host IP: 127.0.1.1
raja
Published on 25-Apr-2019 14:18:30
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