I have some simple single file console programs that demonstrate datagram Client, datagram Server, and a special program that most of you probably are aware of known as ping. All of these programs need wsock32.lib to be added to the project settings link tab properties. Without much commentary, here are the programs:
//-------
//
// DClient.cpp
//
// Extremely simple, totally useless datagram client example.
// Works in conjunction with DServer.cpp.
//
// The program attempts to connect to the server and port
// specified on the command line. The DServer program prints
// the needed information when it is started. Once connected,
// the program sends data to the server, waits for a response
// and then exits.
//
// Compile and link with wsock32.lib
//
// Pass the server name and port number on the command line.
//
// Example: DClient MyMachineName 2000
//
#include <stdio.h>
#include <string.h>
#include <winsock.h>
// Function prototype
void DatagramClient(char *szServer, short nPort);
// Helper macro for displaying errors
#define PRINTERROR(s) \
fprintf(stderr,"\n%: %d\n", s, WSAGetLastError())
////////////////////////////////////////////////////////////
void main(int argc, char **argv)
{
WORD wVersionRequested = MAKEWORD(1,1);
WSADATA wsaData;
int nRet;
short nPort;
//
// Check for the host and port arguments
//
if (argc != 3)
{
fprintf(stderr,"\nSyntax: dclient ServerName PortNumber\n");
return;
}
nPort = atoi(argv[2]);
//
// Initialize WinSock and check the version
//
nRet = WSAStartup(wVersionRequested, &wsaData);
if (wsaData.wVersion != wVersionRequested)
{
fprintf(stderr,"\n Wrong version\n");
return;
}
//
// Go do all the stuff a datagram client does
//
DatagramClient(argv[1], nPort);
//
// Release WinSock
//
WSACleanup();
}
////////////////////////////////////////////////////////////
void DatagramClient(char *szServer, short nPort)
{
printf("\nDatagram Client sending to server: %s on port: %d",
szServer, nPort);
//
// Find the server
//
LPHOSTENT lpHostEntry;
lpHostEntry = gethostbyname(szServer);
if (lpHostEntry == NULL)
{
PRINTERROR("gethostbyname()");
return;
}
//
// Create a UDP/IP datagram socket
//
SOCKET theSocket;
theSocket = socket(AF_INET, // Address family
SOCK_DGRAM, // Socket type
IPPROTO_UDP); // Protocol
if (theSocket == INVALID_SOCKET)
{
PRINTERROR("socket()");
return;
}
//
// Fill in the address structure for the server
//
SOCKADDR_IN saServer;
saServer.sin_family = AF_INET;
saServer.sin_addr = *((LPIN_ADDR)*lpHostEntry->h_addr_list);
// ^ Server's address
saServer.sin_port = htons(nPort); // Port number from command line
//
// Send data to the server
//
char szBuf[256];
int nRet;
strcpy(szBuf, "From the Client");
nRet = sendto(theSocket, // Socket
szBuf, // Data buffer
strlen(szBuf), // Length of data
0, // Flags
(LPSOCKADDR)&saServer, // Server address
sizeof(struct sockaddr)); // Length of address
if (nRet == SOCKET_ERROR)
{
PRINTERROR("sendto()");
closesocket(theSocket);
return;
}
//
// Wait for the reply
//
memset(szBuf, 0, sizeof(szBuf));
int nFromLen;
nFromLen = sizeof(struct sockaddr);
recvfrom(theSocket, // Socket
szBuf, // Receive buffer
sizeof(szBuf), // Length of receive buffer
0, // Flags
(LPSOCKADDR)&saServer, // Buffer to receive sender's address
&nFromLen); // Length of address buffer
if (nRet == SOCKET_ERROR)
{
PRINTERROR("recvfrom()");
closesocket(theSocket);
return;
}
//
// Display the data that was received
//
printf("\nData received: %s", szBuf);
closesocket(theSocket);
return;
}
//------
//-------
//
// DServer.cpp
//
// Extremely simple, totally useless datagram server example.
// Works in conjunction with DClient.cpp.
//
// The program sets itself up as a server using the UDP
// protoocl. It waits for data from a client, displays
// the incoming data, sends a message back to the client
// and then exits.
//
// Compile and link with wsock32.lib
//
// Pass the port number that the server should bind() to
// on the command line. Any port number not already in use
// can be specified.
//
// Example: DServer 2000
//
#include <stdio.h>
#include <winsock.h>
// Function prototype
void DatagramServer(short nPort);
// Helper macro for displaying errors
#define PRINTERROR(s) \
fprintf(stderr,"\n%: %d\n", s, WSAGetLastError())
////////////////////////////////////////////////////////////
void main(int argc, char **argv)
{
WORD wVersionRequested = MAKEWORD(1,1);
WSADATA wsaData;
int nRet;
short nPort;
//
// Check for port argument
//
if (argc != 2)
{
fprintf(stderr,"\nSyntax: dserver PortNumber\n");
return;
}
nPort = atoi(argv[1]);
//
// Initialize WinSock and check version
//
nRet = WSAStartup(wVersionRequested, &wsaData);
if (wsaData.wVersion != wVersionRequested)
{
fprintf(stderr,"\n Wrong version\n");
return;
}
//
// Do all the stuff a datagram server does
//
DatagramServer(nPort);
//
// Release WinSock
//
WSACleanup();
}
////////////////////////////////////////////////////////////
void DatagramServer(short nPort)
{
//
// Create a UDP/IP datagram socket
//
SOCKET theSocket;
theSocket = socket(AF_INET, // Address family
SOCK_DGRAM, // Socket type
IPPROTO_UDP);// Protocol
if (theSocket == INVALID_SOCKET)
{
PRINTERROR("socket()");
return;
}
//
// Fill in the address structure
//
SOCKADDR_IN saServer;
saServer.sin_family = AF_INET;
saServer.sin_addr.s_addr = INADDR_ANY; // Let WinSock assign address
saServer.sin_port = htons(nPort); // Use port passed from user
//
// bind the name to the socket
//
int nRet;
nRet = bind(theSocket, // Socket descriptor
(LPSOCKADDR)&saServer, // Address to bind to
sizeof(struct sockaddr) // Size of address
);
if (nRet == SOCKET_ERROR)
{
PRINTERROR("bind()");
closesocket(theSocket);
return;
}
//
// This isn't normally done or required, but in this
// example we're printing out where the server is waiting
// so that you can connect the example client.
//
int nLen;
nLen = sizeof(SOCKADDR);
char szBuf[256];
nRet = gethostname(szBuf, sizeof(szBuf));
if (nRet == SOCKET_ERROR)
{
PRINTERROR("gethostname()");
closesocket(theSocket);
return;
}
//
// Show the server name and port number
//
printf("\nServer named %s waiting on port %d\n",
szBuf, nPort);
//
// Wait for data from the client
//
SOCKADDR_IN saClient;
memset(szBuf, 0, sizeof(szBuf));
nRet = recvfrom(theSocket, // Bound socket
szBuf, // Receive buffer
sizeof(szBuf), // Size of buffer in bytes
0, // Flags
(LPSOCKADDR)&saClient, // Buffer to receive client address
&nLen); // Length of client address buffer
//
// Show that we've received some data
//
printf("\nData received: %s", szBuf);
//
// Send data back to the client
//
strcpy(szBuf, "From the Server");
sendto(theSocket, // Bound socket
szBuf, // Send buffer
strlen(szBuf), // Length of data to be sent
0, // Flags
(LPSOCKADDR)&saClient, // Address to send data to
nLen); // Length of address
//
// Normally a server continues to run so that
// it is available to other clients. In this
// example, we exit as soon as one transaction
// has taken place.
//
closesocket(theSocket);
return;
}
//------
//---------
//
// Ping.h
//
#pragma pack(1)
#define ICMP_ECHOREPLY 0
#define ICMP_ECHOREQ 8
// IP Header -- RFC 791
typedef struct tagIPHDR
{
u_char VIHL; // Version and IHL
u_char TOS; // Type Of Service
short TotLen; // Total Length
short ID; // Identification
short FlagOff; // Flags and Fragment Offset
u_char TTL; // Time To Live
u_char Protocol; // Protocol
u_short Checksum; // Checksum
struct in_addr iaSrc; // Internet Address - Source
struct in_addr iaDst; // Internet Address - Destination
}IPHDR, *PIPHDR;
// ICMP Header - RFC 792
typedef struct tagICMPHDR
{
u_char Type; // Type
u_char Code; // Code
u_short Checksum; // Checksum
u_short ID; // Identification
u_short Seq; // Sequence
char Data; // Data
}ICMPHDR, *PICMPHDR;
#define REQ_DATASIZE 32 // Echo Request Data size
// ICMP Echo Request
typedef struct tagECHOREQUEST
{
ICMPHDR icmpHdr;
DWORD dwTime;
char cData[REQ_DATASIZE];
}ECHOREQUEST, *PECHOREQUEST;
// ICMP Echo Reply
typedef struct tagECHOREPLY
{
IPHDR ipHdr;
ECHOREQUEST echoRequest;
char cFiller[256];
}ECHOREPLY, *PECHOREPLY;
#pragma pack()
//---------
//-------
//
// PING.C -- Ping program using ICMP and RAW Sockets
//
#include <stdio.h>
#include <stdlib.h>
#include <winsock.h>
#include "ping.h"
// Internal Functions
void Ping(LPCSTR pstrHost);
void ReportError(LPCSTR pstrFrom);
int WaitForEchoReply(SOCKET s);
u_short in_cksum(u_short *addr, int len);
// ICMP Echo Request/Reply functions
int SendEchoRequest(SOCKET, LPSOCKADDR_IN);
DWORD RecvEchoReply(SOCKET, LPSOCKADDR_IN, u_char *);
// main()
void main(int argc, char **argv)
{
WSADATA wsaData;
WORD wVersionRequested = MAKEWORD(1,1);
int nRet;
// Check arguments
if (argc != 2)
{
fprintf(stderr,"\nUsage: ping hostname\n");
return;
}
// Init WinSock
nRet = WSAStartup(wVersionRequested, &wsaData);
if (nRet)
{
fprintf(stderr,"\nError initializing WinSock\n");
return;
}
// Check version
if (wsaData.wVersion != wVersionRequested)
{
fprintf(stderr,"\nWinSock version not supported\n");
return;
}
// Go do the ping
Ping(argv[1]);
// Free WinSock
WSACleanup();
}
// Ping()
// Calls SendEchoRequest() and
// RecvEchoReply() and prints results
void Ping(LPCSTR pstrHost)
{
SOCKET rawSocket;
LPHOSTENT lpHost;
struct sockaddr_in saDest;
struct sockaddr_in saSrc;
DWORD dwTimeSent;
DWORD dwElapsed;
u_char cTTL;
int nLoop;
int nRet;
// Create a Raw socket
rawSocket = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
if (rawSocket == SOCKET_ERROR)
{
ReportError("socket()");
return;
}
// Lookup host
lpHost = gethostbyname(pstrHost);
if (lpHost == NULL)
{
fprintf(stderr,"\nHost not found: %s\n", pstrHost);
return;
}
// Setup destination socket address
saDest.sin_addr.s_addr = *((u_long FAR *) (lpHost->h_addr));
saDest.sin_family = AF_INET;
saDest.sin_port = 0;
// Tell the user what we're doing
printf("\nPinging %s [%s] with %d bytes of data:\n",
pstrHost,
inet_ntoa(saDest.sin_addr),
REQ_DATASIZE);
// Ping multiple times
for (nLoop = 0; nLoop < 4; nLoop++)
{
// Send ICMP echo request
SendEchoRequest(rawSocket, &saDest);
// Use select() to wait for data to be received
nRet = WaitForEchoReply(rawSocket);
if (nRet == SOCKET_ERROR)
{
ReportError("select()");
break;
}
if (!nRet)
{
printf("\nTimeOut");
break;
}
// Receive reply
dwTimeSent = RecvEchoReply(rawSocket, &saSrc, &cTTL);
// Calculate elapsed time
dwElapsed = GetTickCount() - dwTimeSent;
printf("\nReply from: %s: bytes=%d time=%ldms TTL=%d",
inet_ntoa(saSrc.sin_addr),
REQ_DATASIZE,
dwElapsed,
cTTL);
}
printf("\n");
nRet = closesocket(rawSocket);
if (nRet == SOCKET_ERROR)
ReportError("closesocket()");
}
// SendEchoRequest()
// Fill in echo request header
// and send to destination
int SendEchoRequest(SOCKET s,LPSOCKADDR_IN lpstToAddr)
{
static ECHOREQUEST echoReq;
static nId = 1;
static nSeq = 1;
int nRet;
// Fill in echo request
echoReq.icmpHdr.Type = ICMP_ECHOREQ;
echoReq.icmpHdr.Code = 0;
echoReq.icmpHdr.Checksum = 0;
echoReq.icmpHdr.ID = nId++;
echoReq.icmpHdr.Seq = nSeq++;
// Fill in some data to send
for (nRet = 0; nRet < REQ_DATASIZE; nRet++)
echoReq.cData[nRet] = ' '+nRet;
// Save tick count when sent
echoReq.dwTime = GetTickCount();
// Put data in packet and compute checksum
echoReq.icmpHdr.Checksum = in_cksum((u_short *)&echoReq, sizeof(ECHOREQUEST));
// Send the echo request
nRet = sendto(s, /* socket */
(LPSTR)&echoReq, /* buffer */
sizeof(ECHOREQUEST),
0, /* flags */
(LPSOCKADDR)lpstToAddr, /* destination */
sizeof(SOCKADDR_IN)); /* address length */
if (nRet == SOCKET_ERROR)
ReportError("sendto()");
return (nRet);
}
// RecvEchoReply()
// Receive incoming data
// and parse out fields
DWORD RecvEchoReply(SOCKET s, LPSOCKADDR_IN lpsaFrom, u_char *pTTL)
{
ECHOREPLY echoReply;
int nRet;
int nAddrLen = sizeof(struct sockaddr_in);
// Receive the echo reply
nRet = recvfrom(s, // socket
(LPSTR)&echoReply, // buffer
sizeof(ECHOREPLY), // size of buffer
0, // flags
(LPSOCKADDR)lpsaFrom, // From address
&nAddrLen); // pointer to address len
// Check return value
if (nRet == SOCKET_ERROR)
ReportError("recvfrom()");
// return time sent and IP TTL
*pTTL = echoReply.ipHdr.TTL;
return(echoReply.echoRequest.dwTime);
}
// What happened?
void ReportError(LPCSTR pWhere)
{
fprintf(stderr,"\n%s error: %d\n",
WSAGetLastError());
}
// WaitForEchoReply()
// Use select() to determine when
// data is waiting to be read
int WaitForEchoReply(SOCKET s)
{
struct timeval Timeout;
fd_set readfds;
readfds.fd_count = 1;
readfds.fd_array[0] = s;
Timeout.tv_sec = 5;
Timeout.tv_usec = 0;
return(select(1, &readfds, NULL, NULL, &Timeout));
}
//
// Mike Muuss' in_cksum() function
// and his comments from the original
// ping program
//
// * Author -
// * Mike Muuss
// * U. S. Army Ballistic Research Laboratory
// * December, 1983
/*
* I N _ C K S U M
*
* Checksum routine for Internet Protocol family headers (C Version)
*
*/
u_short in_cksum(u_short *addr, int len)
{
register int nleft = len;
register u_short *w = addr;
register u_short answer;
register int sum = 0;
/*
* Our algorithm is simple, using a 32 bit accumulator (sum),
* we add sequential 16 bit words to it, and at the end, fold
* back all the carry bits from the top 16 bits into the lower
* 16 bits.
*/
while( nleft > 1 ) {
sum += *w++;
nleft -= 2;
}
/* mop up an odd byte, if necessary */
if( nleft == 1 ) {
u_short u = 0;
*(u_char *)(&u) = *(u_char *)w ;
sum += u;
}
/*
* add back carry outs from top 16 bits to low 16 bits
*/
sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
sum += (sum >> 16); /* add carry */
answer = ~sum; /* truncate to 16 bits */
return (answer);
}
//------