ICMP Ping Program in C

This sample C program demonstrates how an ICMP ping app can be written using the SOCK_RAW socket type and IPPROTO_ICMP protocol. ICMP or Internet Control Message Protocol is used by network devices to measure round-trip-delays and packet loss across network paths.

Ping is a necessary tool in any Operating System to debug the IP address of the network device to see if the device is reachable.

By creating a raw socket, the underlying layer does not change the protocol header. When we submit the ICMP header, nothing is adjusted so that the receiving end will see an ICMP packet. Additionally, we use the record route IP option to get a round trip path to the endpoint. Ping sends out ICMP packets by opening a RAW socket, which is separate from TCP and UDP.

Note that the size of the IP option header that records the route is limited to nine IP addresses.

Internet Control Message Protocol (ICMP) Ping – C Program

Compile the Ping program

This program is modified to work fine with Visual Studio in Windows 11. It compiles successfully both with 32 and 64 bit versions of the OS.

If you want to use Visual Studio Developer command line to compile the Ping program, use the following command. Read more about compiling C/C++ Program from command line here. You can also use any other C/C++ compilers to build and run this program.

C:\Users\ping>cl /EHsc ping.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 19.16.27035 for x86
Copyright (C) Microsoft Corporation.  All rights reserved.

ping.cpp
Microsoft (R) Incremental Linker Version 14.16.27035.0
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:ping.exe
ping.obj

Run the Ping Program

This C Program has the following Command Line Options and Parameters.

Ping [host] [packet-size]

Host String name of host to ping

packet-size Integer size of packet to send (smaller than 1024 bytes)

C:\Users\ping>ping.exe 127.0.0.1 64
dest.sin_addr = 192.168.56.1
96 bytes from 192.168.56.1: icmp_seq = 0.  time: 0 ms
96 bytes from 192.168.56.1: icmp_seq = 1.  time: 0 ms
96 bytes from 192.168.56.1: icmp_seq = 2.  time: 0 ms
96 bytes from 192.168.56.1: icmp_seq = 3.  time: 0 ms

You can use this program to ping internet addresses such as google.com

C:\Users\ping>ping.exe www.google.com 64
dest.sin_addr = 172.217.21.36
96 bytes from 172.217.21.36: icmp_seq = 0.  time: 31 ms
96 bytes from 172.217.21.36: icmp_seq = 1.  time: 47 ms
96 bytes from 172.217.21.36: icmp_seq = 2.  time: 47 ms
96 bytes from 172.217.21.36: icmp_seq = 3.  time: 31 ms

Ping C Program Source Code

Below is the full source code you can use. Alternatively, you can download the complete Visual Studio 2017 C++ Solution file here:

  Ping C Program (7.1 KiB, 4,038 hits)

// Module Name: Ping.c
//
// Description:
//    This sample illustrates how an ICMP ping app can be written
//    using the SOCK_RAW socket type and IPPROTO_ICMP protocol.
//    By creating a raw socket, the underlying layer does not change
//    the protocol header so that when we submit the ICMP header
//    nothing is changed so that the receiving end will see an
//    ICMP packet. Additionally, we use the record route IP option
//    to get a round trip path to the endpoint. Note that the size
//    of the IP option header that records the route is limited to
//    nine IP addresses.
//
// Compile:
//     cl -o Ping Ping.c ws2_32.lib /Zp1
//
// Command Line Options/Parameters:
//     Ping [host] [packet-size]
//
//     host         String name of host to ping
//     packet-size  Integer size of packet to send
//                      (smaller than 1024 bytes)
//
//#pragma pack(1)

#define WIN32_LEAN_AND_MEAN

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#pragma comment(lib, "Ws2_32.lib")

#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <stdlib.h>

#define IP_RECORD_ROUTE  0x7
//
// IP header structure
//
typedef struct _iphdr
{
 unsigned int   h_len : 4;        // Length of the header
 unsigned int   version : 4;      // Version of IP
 unsigned char  tos;            // Type of service
 unsigned short total_len;      // Total length of the packet
 unsigned short ident;          // Unique identifier
 unsigned short frag_and_flags; // Flags
 unsigned char  ttl;            // Time to live
 unsigned char  proto;          // Protocol (TCP, UDP etc)
 unsigned short checksum;       // IP checksum

 unsigned int   sourceIP;
 unsigned int   destIP;
} IpHeader;

#define ICMP_ECHO        8
#define ICMP_ECHOREPLY   0
#define ICMP_MIN         8 // Minimum 8-byte ICMP packet (header)

//
// ICMP header structure
//
typedef struct _icmphdr
{
 BYTE   i_type;
 BYTE   i_code;                 // Type sub code
 USHORT i_cksum;
 USHORT i_id;
 USHORT i_seq;
 // This is not the standard header, but we reserve space for time
 ULONG  timestamp;
} IcmpHeader;

//
// IP option header - use with socket option IP_OPTIONS
//
typedef struct _ipoptionhdr
{
 unsigned char        code;        // Option type
 unsigned char        len;         // Length of option hdr
 unsigned char        ptr;         // Offset into options
 unsigned long        addr[9];     // List of IP addrs
} IpOptionHeader;

#define DEF_PACKET_SIZE  32        // Default packet size
#define MAX_PACKET       1024      // Max ICMP packet size
#define MAX_IP_HDR_SIZE  60        // Max IP header size w/options

BOOL  bRecordRoute;
int   datasize;
char *lpdest;

//
// Function: usage
//
// Description:
//    Print usage information
//
void usage(char *progname)
{
 printf("usage: ping -r  [data size]\n");
 printf("       -r           record route\n");
 printf("        host        remote machine to ping\n");
 printf("        datasize    can be up to 1KB\n");
 ExitProcess(-1);
}

//
// Function: FillICMPData
//
// Description:
//    Helper function to fill in various fields for our ICMP request
//
void FillICMPData(char *icmp_data, int datasize)
{
 IcmpHeader *icmp_hdr = NULL;
 char       *datapart = NULL;

 icmp_hdr = (IcmpHeader*)icmp_data;
 icmp_hdr->i_type = ICMP_ECHO;        // Request an ICMP echo
 icmp_hdr->i_code = 0;
 icmp_hdr->i_id = (USHORT)GetCurrentProcessId();
 icmp_hdr->i_cksum = 0;
 icmp_hdr->i_seq = 0;

 datapart = icmp_data + sizeof(IcmpHeader);
 //
 // Place some junk in the buffer
 //
 memset(datapart, 'E', datasize - sizeof(IcmpHeader));
}

//
// Function: checksum
//
// Description:
//    This function calculates the 16-bit one's complement sum
//    of the supplied buffer (ICMP) header
//
USHORT checksum(USHORT *buffer, int size)
{
 unsigned long cksum = 0;

 while (size > 1)
 {
  cksum += *buffer++;
  size -= sizeof(USHORT);
 }
 if (size)
 {
  cksum += *(UCHAR*)buffer;
 }
 cksum = (cksum >> 16) + (cksum & 0xffff);
 cksum += (cksum >> 16);
 return (USHORT)(~cksum);
}

//
// Function: DecodeIPOptions
//
// Description:
//    If the IP option header is present, find the IP options
//    within the IP header and print the record route option
//    values
//
void DecodeIPOptions(char *buf, int bytes)
{
 IpOptionHeader *ipopt = NULL;
 IN_ADDR         inaddr;
 int             i;
 HOSTENT        *host = NULL;

 ipopt = (IpOptionHeader *)(buf + 20);

 printf("RR:   ");
 for (i = 0; i < (ipopt->ptr / 4) - 1; i++)
 {
  inaddr.S_un.S_addr = ipopt->addr[i];
  if (i != 0)
   printf("      ");
  host = gethostbyaddr((char *)&inaddr.S_un.S_addr,
   sizeof(inaddr.S_un.S_addr), AF_INET);
  if (host)
   printf("(%-15s) %s\n", inet_ntoa(inaddr), host->h_name);
  else
   printf("(%-15s)\n", inet_ntoa(inaddr));
 }
 return;
}

//
// Function: DecodeICMPHeader
//
// Description:
//    The response is an IP packet. We must decode the IP header to
//    locate the ICMP data.
//
void DecodeICMPHeader(char *buf, int bytes,
 struct sockaddr_in *from)
{
 IpHeader       *iphdr = NULL;
 IcmpHeader     *icmphdr = NULL;
 unsigned short  iphdrlen;
 DWORD           tick;
 static   int    icmpcount = 0;

 iphdr = (IpHeader *)buf;
 // Number of 32-bit words * 4 = bytes
 iphdrlen = iphdr->h_len * 4;
 tick = GetTickCount();

 if ((iphdrlen == MAX_IP_HDR_SIZE) && (!icmpcount))
  DecodeIPOptions(buf, bytes);

 if (bytes < iphdrlen + ICMP_MIN) {
  printf("Too few bytes from %s\n", inet_ntoa(from->sin_addr));
 }
 icmphdr = (IcmpHeader*)(buf + iphdrlen);

 if (icmphdr->i_type != ICMP_ECHOREPLY)
 {
  printf("nonecho type %d recvd\n", icmphdr->i_type);
  return;
 }
 // Make sure this is an ICMP reply to something we sent!
 //
 if (icmphdr->i_id != (USHORT)GetCurrentProcessId())
 {
  printf("someone else's packet!\n");
  return;
 }
 printf("%d bytes from %s:", bytes, inet_ntoa(from->sin_addr));
 printf(" icmp_seq = %d. ", icmphdr->i_seq);
 printf(" time: %d ms", tick - icmphdr->timestamp);
 printf("\n");

 icmpcount++;
 return;
}

void ValidateArgs(int argc, char **argv)
{
 int                i;

 bRecordRoute = FALSE;
 lpdest = NULL;
 datasize = DEF_PACKET_SIZE;

 for (i = 1; i < argc; i++) {
  if ((argv[i][0] == '-') || (argv[i][0] == '/')) {
   switch (tolower(argv[i][1])) {
   case 'r': // Record route option 
    bRecordRoute = TRUE;
    break;
   default:
    usage(argv[0]); break;
   }
  }
  else if (isdigit(argv[i][0]))
   datasize = atoi(argv[i]);
  else lpdest = argv[i];
 }
}

// 
// Function: main 
// 
// Description: 
// Setup the ICMP raw socket, and create the ICMP header. Add 
// the appropriate IP option header, and start sending ICMP 
// echo requests to the endpoint. For each send and receive, 
// we set a timeout value so that we don't wait forever for a 
// response in case the endpoint is not responding. When we 
// receive a packet decode it. 
// 
int main(int argc, char **argv) {
 WSADATA wsaData;
 SOCKET sockRaw = INVALID_SOCKET;
 struct sockaddr_in dest, from;
 int bread, fromlen = sizeof(from), timeout = 1000, ret;
 char *icmp_data = NULL, *recvbuf = NULL;
 unsigned int addr = 0;
 USHORT seq_no = 0;
 struct hostent *hp = NULL;
 IpOptionHeader ipopt;
 if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
  printf("WSAStartup() failed: %d\n", GetLastError());
  return -1;
 }

 ValidateArgs(argc, argv);
 // 
 // WSA_FLAG_OVERLAPPED flag is required for SO_RCVTIMEO, 
 // SO_SNDTIMEO option. If NULL is used as last param for 
 // WSASocket, all I/O on the socket is synchronous, the 
 // internal user mode wait code never gets a chance to 
 // execute, and therefore kernel-mode I/O blocks forever. 
 // A socket created via the socket function has the over- 
 // lapped I/O attribute set internally. But here we need
 // to use WSASocket to specify a raw socket. 
 // 
 // If you want to use timeout with a synchronous 
 // nonoverlapped socket created by WSASocket with last 
 // param set to NULL, you can set the timeout by using 
 // the select function, or you can use WSAEventSelect and 
 // set the timeout in the WSAWaitForMultipleEvents 
 // function. 
 // 
 sockRaw = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0, WSA_FLAG_OVERLAPPED);
 if (sockRaw == INVALID_SOCKET) {
  printf("WSASocket() failed: %d\n", WSAGetLastError());
  return -1;
 }
 if (bRecordRoute) {
  // Setup the IP option header to go out on every ICMP packet 
  // 
  ZeroMemory(&ipopt, sizeof(ipopt));
  ipopt.code = IP_RECORD_ROUTE;
  // Record route option 
  ipopt.ptr = 4;
  // Point to the first addr offset 
  ipopt.len = 39;
  // Length of option header 
  ret = setsockopt(sockRaw, IPPROTO_IP, IP_OPTIONS, (char *)&ipopt, sizeof(ipopt));
  if (ret == SOCKET_ERROR) {
   printf("setsockopt(IP_OPTIONS) failed: %d\n", WSAGetLastError());
  }
 }
 // Set the send/recv timeout values 
 // 
 bread = setsockopt(sockRaw, SOL_SOCKET, SO_RCVTIMEO, (char*)&timeout, sizeof(timeout));
 if (bread == SOCKET_ERROR)
 {
  printf("setsockopt(SO_RCVTIMEO) failed: %d\n", WSAGetLastError());
  return -1;
 }
 timeout = 1000;
 bread = setsockopt(sockRaw, SOL_SOCKET, SO_SNDTIMEO, (char*)&timeout, sizeof(timeout));
 if (bread == SOCKET_ERROR)
 {
  printf("setsockopt(SO_SNDTIMEO) failed: %d\n", WSAGetLastError());
  return -1;
 }
 memset(&dest, 0, sizeof(dest));

 // 
 // Resolve the endpoint's name if necessary 
 // 
 dest.sin_family = AF_INET;
 if ((dest.sin_addr.s_addr = inet_addr(lpdest)) == INADDR_NONE)
 {
  if ((hp = gethostbyname(lpdest)) != NULL)
  {
   memcpy(&(dest.sin_addr), hp->h_addr, hp->h_length);
   dest.sin_family = hp->h_addrtype;
   printf("dest.sin_addr = %s\n", inet_ntoa(dest.sin_addr));
  }
  else
  {
   printf("gethostbyname() failed: %d\n",
    WSAGetLastError());
   return -1;
  }
 }

 //
 // Create the ICMP packet
 //
 datasize += sizeof(IcmpHeader);

 icmp_data = (char *) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, MAX_PACKET);
 recvbuf = (char *) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, MAX_PACKET);
 if (!icmp_data)
 {
  printf("HeapAlloc() failed: %d\n", GetLastError());
  return -1;
 }
 memset(icmp_data, 0, MAX_PACKET);
 FillICMPData(icmp_data, datasize);
 //
 // Start sending/receiving ICMP packets
 //
 while (1)
 {
  static int nCount = 0;
  int        bwrote;

  if (nCount++ == 4)
   break;

  ((IcmpHeader*)icmp_data)->i_cksum = 0;
  ((IcmpHeader*)icmp_data)->timestamp = GetTickCount();
  ((IcmpHeader*)icmp_data)->i_seq = seq_no++;
  ((IcmpHeader*)icmp_data)->i_cksum =
   checksum((USHORT*)icmp_data, datasize);

  bwrote = sendto(sockRaw, icmp_data, datasize, 0,
   (struct sockaddr*)&dest, sizeof(dest));
  if (bwrote == SOCKET_ERROR)
  {
   if (WSAGetLastError() == WSAETIMEDOUT)
   {
    printf("timed out\n");
    continue;
   }
   printf("sendto() failed: %d\n", WSAGetLastError());
   return -1;
  }
  if (bwrote < datasize)
  {
   printf("Wrote %d bytes\n", bwrote);
  }
  bread = recvfrom(sockRaw, recvbuf, MAX_PACKET, 0,
   (struct sockaddr*)&from, &fromlen);
  if (bread == SOCKET_ERROR)
  {
   if (WSAGetLastError() == WSAETIMEDOUT)
   {
    printf("timed out\n");
    continue;
   }
   printf("recvfrom() failed: %d\n", WSAGetLastError());
   return -1;
  }
  DecodeICMPHeader(recvbuf, bread, &from);

  Sleep(1000);
 }
 // Cleanup
 //
 if (sockRaw != INVALID_SOCKET)
  closesocket(sockRaw);
 HeapFree(GetProcessHeap(), 0, recvbuf);
 HeapFree(GetProcessHeap(), 0, icmp_data);

 WSACleanup();
 return 0;
}