qping.cpp

See Appendix B for a description of the programs included on this companion disk. RESOURCE.WRI iden

#include	"..\winsock.h"					// Winsock header file

#define PROG_NAME "A Simple Ping Program"

#define HOST_NAME "cerfnet.com"		// This can be any valid host name
#define WINSOCK_VERSION 0x0101		// Program requires Winsock version 1.1
#define NO_FLAGS 0								// No special flags specified
																	// RFC 792 defines ICMP message values
#define ICMP_ECHO 8								// An ICMP echo message
#define ICMP_ECHOREPLY 0					// An ICMP echo reply message
#define	ICMP_HEADERSIZE 8					// ICMP header size ("echo messages" only)

struct ip 												// Structure for IP datagram header
	{
		BYTE ip_verlen;								// Version and header length
		BYTE ip_tos;									// Type of service
		WORD ip_len;									// Total packet length 
		UINT ip_id;										// Datagram identification 
		WORD ip_fragoff;							// Fragment offset 
		BYTE ip_ttl;									// Time to live 
		BYTE ip_proto;								// Protocol
		UINT ip_chksum;								// Checksum 
		IN_ADDR ip_src_addr;					// Source address 
		IN_ADDR ip_dst_addr;					// Destination address 
		BYTE ip_data[1];							// Variable length data area
	};
			
struct icmp												// Structure for an ICMP header
	{
		BYTE icmp_type;								// Type of message
		BYTE icmp_code;								// Type "sub code" (zero for echos)
		WORD icmp_cksum;							// 1's complement checksum
		WORD icmp_id;									// Unique ID (the instance handle)
		WORD icmp_seq;								// Tracks multiple pings
		BYTE icmp_data[1];						// The start of optional data
	};

char szPingBuffer[100];						// General purpose buffer for messages

WORD InternetChksum(LPWORD lpwIcmpData, WORD wDataLength)
	{
		long	lSum;				// Store the summation
		WORD	wOddByte;		// Left over byte from the summation
		WORD	wAnswer;		// The 1's complement checksum
		
		lSum = 0L;

		while (wDataLength > 1)
			{
				lSum += *lpwIcmpData++;
				wDataLength -= 2;
			}

		// Handle the odd byte if necessary and make sure the top half is zero
		if (wDataLength == 1)
			{
				wOddByte = 0;
				*((LPBYTE) &wOddByte) = *(LPBYTE)lpwIcmpData;	// One byte only
				lSum += wOddByte;
			}

		// Add back the carry outs from the 16 bits to the low 16 bits
		lSum = (lSum >> 16) + (lSum & 0xffff);	// Add high-16 to low-16
		lSum += (lSum >> 16);										// Add carry
		wAnswer = (WORD)~lSum;									// 1's complement, then truncate 
																						// to 16 bits
		return(wAnswer);
	}

BOOL DoPingOperation(HANDLE hInstance)
	{
																	// Local variables
		int iPacketSize;							// ICMP packet size 
		int iHostAddrLength;					// Host address length
		int iIPHeadLength;						// IP datagram header length
		int iReceivedBytes;						// Number of bytes received
		int iSentBytes;								// Number of bytes sent
		int nProtocol;								// ICMP protocol number
		int iSocketError;							// Stores any error codes
		PDWORD pdwTimeStamp;					// Tick count at transmission
		DWORD dwReturnTime;						// Tick count upon receipt of echo reply
		DWORD dwRoundTrip;						// Tick count for the round-trip
																	// Structures defined in WINSOCK.H
		SOCKADDR_IN	sockAddrLocal;		// Socket address structures
		SOCKADDR_IN	sockAddrHost;			// 
		SOCKET hSocket;								// Socket handle (or descriptor)
		LPHOSTENT lpHostEntry;				// Internet host data structure
		LPPROTOENT lpProtocolEntry;		// Internet protocol data structure

		BYTE IcmpSendPacket[1024];		// Buffer space for data to send
		BYTE IcmpRecvPacket[4096];		// Buffer space for received data 

		struct icmp *pIcmpHeader;			// A pointer to the ICMP structure
		struct ip *pIpHeader;					// A pointer to the IP header structure
		LPSTR lpszHostName;						// A pointer to the time server host
		
		lpszHostName = HOST_NAME;

		if ((lpHostEntry = gethostbyname(HOST_NAME)) == NULL)
			{
				wsprintf(szPingBuffer, "Could not get %s IP address.",
							(LPSTR)lpszHostName);
				return(FALSE);
			}
    
		sockAddrLocal.sin_family = AF_INET;
		sockAddrLocal.sin_addr = *((LPIN_ADDR) *lpHostEntry->h_addr_list);

		// With a raw socket, the program must specify a protocol
		if ((lpProtocolEntry = getprotobyname("icmp")) == NULL)
			nProtocol = IPPROTO_ICMP;
		else
			nProtocol = lpProtocolEntry->p_proto;
		
		// Create a "raw" socket and specify ICMP as the protocol to use
		if ((hSocket = socket(PF_INET, SOCK_RAW, nProtocol)) == 
					INVALID_SOCKET)
			{
				wsprintf(szPingBuffer, "Could not create a RAW socket.");
				return(FALSE);
			}

		pIcmpHeader = (struct icmp *) IcmpSendPacket;	// Point at the data area
		pIcmpHeader->icmp_type = ICMP_ECHO;						// then fill in the data.
		pIcmpHeader->icmp_code = 0;										// Use the Sockman instance 
		pIcmpHeader->icmp_id = hInstance;							// handle as a unique ID.
		pIcmpHeader->icmp_seq = 0;										// It's important to reset
		pIcmpHeader->icmp_cksum = 0;									// the checksum to zero.
		
		//Put tick count in the optional data area
		pdwTimeStamp = (PDWORD)&IcmpSendPacket[ICMP_HEADERSIZE];
		*pdwTimeStamp = GetTickCount();
		iPacketSize = ICMP_HEADERSIZE + sizeof(DWORD);
		pIcmpHeader->icmp_cksum = InternetChksum((LPWORD)pIcmpHeader, 
					iPacketSize);
    
		if (pIcmpHeader->icmp_cksum !=0 )
			{    
				iSentBytes = sendto(hSocket, (LPSTR) IcmpSendPacket, iPacketSize, 
							NO_FLAGS, (LPSOCKADDR) &sockAddrLocal, sizeof(sockAddrLocal));
				if (iSentBytes == SOCKET_ERROR)
					{
						closesocket(hSocket);
						wsprintf(szPingBuffer,
									"The sendto() function returned a socket error.");
						return(FALSE);
					}
		
				if (iSentBytes != iPacketSize)
					{
						closesocket(hSocket);
						wsprintf(szPingBuffer,
									"Wrong number of bytes sent: %d", iSentBytes);
						return(FALSE);
					}
		
				iHostAddrLength = sizeof(sockAddrHost);
		
				iReceivedBytes = recvfrom(hSocket, (LPSTR) IcmpRecvPacket, 
							sizeof(IcmpRecvPacket), NO_FLAGS, (LPSOCKADDR) &sockAddrHost,
							&iHostAddrLength);
			}
		else
			{
				closesocket(hSocket);
				wsprintf(szPingBuffer,
							"Checksum computation error! Result was zero!");
				return(FALSE);
			}
    
		closesocket(hSocket);
		
		if (iReceivedBytes == SOCKET_ERROR)
			{   
				iSocketError = WSAGetLastError();
				if (iSocketError == 10004)
					{
						wsprintf(szPingBuffer,
									"Ping operation for %s was cancelled.", 
									(LPSTR)lpszHostName);
						dwRoundTrip = 0;
						return(TRUE);
					}
				else
					{
						wsprintf(szPingBuffer,
									"Socket Error from recvfrom(): %d", iSocketError);
						return(FALSE);
					}
			}

		dwReturnTime = GetTickCount();
		dwRoundTrip = dwReturnTime - *pdwTimeStamp;

		// Point to the IP Header in the received packet
		pIpHeader = (struct ip *)IcmpRecvPacket;

		// Extract bits 4-7 and convert the number of 32-bit words to bytes
		iIPHeadLength = (pIpHeader->ip_verlen >> 4) << 2;

		// Test the length to make sure an ICMP header was received
		if (iReceivedBytes < iIPHeadLength + ICMP_HEADERSIZE)
			{
				wsprintf(szPingBuffer, "Received packet was too short.");
				return(FALSE);
			}

		// Point to the ICMP message which immediately follows the IP header
		pIcmpHeader = (struct icmp *) (IcmpRecvPacket + iIPHeadLength);

		// Make sure this is an ICMP "echo reply"
		if (pIcmpHeader->icmp_type != ICMP_ECHOREPLY)
			{
				wsprintf(szPingBuffer,
							"Received packet was not an echo reply to your ping.");
				return(FALSE);
			}

		// Make sure this program sent the packet
		if (pIcmpHeader->icmp_id != (WORD)hInstance)
			{
				wsprintf(szPingBuffer,
							"Received packet was not sent by this program.");
				return(FALSE);
			}

		// This appears to be a matching reply. Note the IP address and 
		// host name that sent the ICMP echo reply message.
		lstrcpy(lpszHostName, (LPSTR)lpHostEntry->h_name);
		wsprintf(szPingBuffer,
					"Round-trip travel time to %s [%s] was %d milliseconds.",
					(LPSTR)lpszHostName, (LPSTR)inet_ntoa(sockAddrHost.sin_addr), 
					dwRoundTrip);
		
		return(TRUE); 
	}

int PASCAL WinMain(HANDLE hInstance, HANDLE hPrevInstance, 
			LPSTR lpszCmdParam, int nCmdShow)
	{
		WSADATA wsaData;							// Winsock implementation details

		// Start the program here
		WSAStartup(WINSOCK_VERSION, &wsaData);
		
		DoPingOperation(hInstance);
		MessageBox(NULL, szPingBuffer, PROG_NAME, MB_OK|MB_ICONSTOP);

		WSACleanup();
		return(NULL); 
	}