Sender Program (sender.c):
The sender program is a UDP datagram sender that can be configured through command line options. It initializes Winsock, creates a UDP socket, and either connects to a recipient’s IP address or uses sendto() to send datagram messages. The program allows customization of parameters such as the remote port, recipient’s IP address, message count, buffer size, and the character used to fill the buffer.
Compile:
cl -o Sender Sender.c ws2_32.lib
Command line options:
sender [-p:int] [-r:IP] [-c] [-n:x] [-b:x] [-d:c]
-p:int Remote port
-r:IP Recipient’s IP address or hostname
-c Connect to remote IP first
-n:x Number of times to send message
-b:x Size of buffer to send
-d:c Character to fill buffer with
Receiver Program (receiver.c):
The receiver program complements the sender by receiving UDP datagrams. It initializes Winsock, creates a UDP socket, binds to a specified local IP and port, and enters a loop to continuously receive datagram messages using recvfrom(). The program supports command line options for configuring the local port, local IP address, and buffer size. Received data can be processed within the loop, making it suitable for handling incoming UDP messages.
Compile:
cl -o Receiver Receiver.c ws2_32.lib
Command line options:
sender [-p:int] [-i:IP][-n:x] [-b:x]
-p:int Local port
-i:IP Local IP address to listen on
-n:x Number of times to send message
-b:x Size of buffer to send
// Module Name: Sender.c
//
// Description:
// This sample sends UDP datagrams to the specified recipient.
// The -c option first calls connect() to associate the
// recipient's IP address with the socket handle so that the
// send() function can be used as opposed to the sendto() call.
//
// Compile:
// cl -o Sender Sender.c ws2_32.lib
//
// Command line options:
// sender [-p:int] [-r:IP] [-c] [-n:x] [-b:x] [-d:c]
// -p:int Remote port
// -r:IP Recipient's IP address or hostname
// -c Connect to remote IP first
// -n:x Number of times to send message
// -b:x Size of buffer to send
// -d:c Character to fill buffer with
//
#include <winsock2.h>
#include <stdio.h>
#include <stdlib.h>
#define DEFAULT_PORT 5150
#define DEFAULT_COUNT 25
#define DEFAULT_CHAR 'a'
#define DEFAULT_BUFFER_LENGTH 64
BOOL bConnect = FALSE; // Connect to recipient first
int iPort = DEFAULT_PORT; // Port to send data to
char cChar = DEFAULT_CHAR; // Character to fill buffer
DWORD dwCount = DEFAULT_COUNT, // Number of messages to send
dwLength = DEFAULT_BUFFER_LENGTH; // Length of buffer to send
char szRecipient[128]; // Recipient's IP or hostname
//
// Function: usage
//
// Description:
// Print usage information and exit
//
void usage()
{
printf("usage: sender [-p:int] [-r:IP] "
"[-c] [-n:x] [-b:x] [-d:c]\n\n");
printf(" -p:int Remote port\n");
printf(" -r:IP Recipients IP address or hostname\n");
printf(" -c Connect to remote IP first\n");
printf(" -n:x Number of times to send message\n");
printf(" -b:x Size of buffer to send\n");
printf(" -d:c Character to fill buffer with\n\n");
ExitProcess(1);
}
//
// Function: ValidateArgs
//
// Description:
// Parse the command line arguments, and set some global flags to
// indicate what actions to perform
//
void ValidateArgs(int argc, char **argv)
{
int i;
for(i = 1; i < argc; i++)
{
if ((argv[i][0] == '-') || (argv[i][0] == '/'))
{
switch (tolower(argv[i][1]))
{
case 'p': // Remote port
if (strlen(argv[i]) > 3)
iPort = atoi(&argv[i][3]);
break;
case 'r': // Recipient's IP addr
if (strlen(argv[i]) > 3)
strcpy(szRecipient, &argv[i][3]);
break;
case 'c': // Connect to recipients IP addr
bConnect = TRUE;
break;
case 'n': // Number of times to send message
if (strlen(argv[i]) > 3)
dwCount = atol(&argv[i][3]);
break;
case 'b': // Buffer size
if (strlen(argv[i]) > 3)
dwLength = atol(&argv[i][3]);
break;
case 'd': // Character to fill buffer
cChar = argv[i][3];
break;
default:
usage();
break;
}
}
}
}
//
// Function: main
//
// Description:
// Main thread of execution. Initialize Winsock, parse the command
// line arguments, create a socket, connect to the remote IP
// address if specified, and then send datagram messages to the
// recipient.
//
int main(int argc, char **argv)
{
WSADATA wsd;
SOCKET s;
char *sendbuf = NULL;
int ret,
i;
SOCKADDR_IN recipient;
// Parse the command line and load Winsock
//
ValidateArgs(argc, argv);
if (WSAStartup(MAKEWORD(2, 2), &wsd) != 0)
{
printf("WSAStartup failed!\n");
return 1;
}
// Create the socket
//
s = socket(AF_INET, SOCK_DGRAM, 0);
if (s == INVALID_SOCKET)
{
printf("socket() failed; %d\n", WSAGetLastError());
return 1;
}
// Resolve the recipient's IP address or hostname
//
recipient.sin_family = AF_INET;
recipient.sin_port = htons((short)iPort);
if ((recipient.sin_addr.s_addr = inet_addr(szRecipient))
== INADDR_NONE)
{
struct hostent *host=NULL;
host = gethostbyname(szRecipient);
if (host)
CopyMemory(&recipient.sin_addr, host->h_addr_list[0],
host->h_length);
else
{
printf("gethostbyname() failed: %d\n", WSAGetLastError());
WSACleanup();
return 1;
}
}
// Allocate the send buffer
//
sendbuf = GlobalAlloc(GMEM_FIXED, dwLength);
if (!sendbuf)
{
printf("GlobalAlloc() failed: %d\n", GetLastError());
return 1;
}
memset(sendbuf, cChar, dwLength);
//
// If the connect option is set, "connect" to the recipient
// and send the data with the send() function
//
if (bConnect)
{
if (connect(s, (SOCKADDR *)&recipient,
sizeof(recipient)) == SOCKET_ERROR)
{
printf("connect() failed: %d\n", WSAGetLastError());
GlobalFree(sendbuf);
WSACleanup();
return 1;
}
for(i = 0; i < dwCount; i++)
{
ret = send(s, sendbuf, dwLength, 0);
if (ret == SOCKET_ERROR)
{
printf("send() failed: %d\n", WSAGetLastError());
break;
}
else if (ret == 0)
break;
// send() succeeded!
}
}
else
{
// Otherwise, use the sendto() function
//
for(i = 0; i < dwCount; i++)
{
ret = sendto(s, sendbuf, dwLength, 0,
(SOCKADDR *)&recipient, sizeof(recipient));
if (ret == SOCKET_ERROR)
{
printf("sendto() failed; %d\n", WSAGetLastError());
break;
}
else if (ret == 0)
break;
// sendto() succeeded!
}
}
closesocket(s);
GlobalFree(sendbuf);
WSACleanup();
return 0;
}
Here is a basic example of a receiver.c program that complements the sender.c program. This receiver program binds to the specified interface and port number and then blocks on a recvfrom() call to receive UDP datagrams:
// Module Name: Receiver.c
//
// Description:
// This sample receives UDP datagrams by binding to
// the specified interface and port number and then blocking on a recvfrom()
// call
//
// Compile:
// cl -o Receiver Receiver.c ws2_32.lib
//
// Command line options:
// receiver [-p:int] [-i:IP] [-b:x]
// -p:int Local port
// -i:IP Local IP address to listen on
// -b:x Size of buffer to receive
//
#include <winsock2.h>
#include <stdio.h>
#include <stdlib.h>
#define DEFAULT_PORT 5150
#define DEFAULT_BUFFER_LENGTH 64
int iPort = DEFAULT_PORT; // Port to receive data on
DWORD dwLength = DEFAULT_BUFFER_LENGTH; // Length of buffer to receive
//
// Function: usage
//
// Description:
// Print usage information and exit
//
void usage()
{
printf("usage: receiver [-p:int] [-i:IP] [-b:x]\n\n");
printf(" -p:int Local port\n");
printf(" -i:IP Local IP address to listen on\n");
printf(" -b:x Size of buffer to receive\n\n");
ExitProcess(1);
}
//
// Function: ValidateArgs
//
// Description:
// Parse the command line arguments and set the global variables
//
void ValidateArgs(int argc, char **argv)
{
int i;
for (i = 1; i < argc; i++)
{
if ((argv[i][0] == '-') || (argv[i][0] == '/'))
{
switch (tolower(argv[i][1]))
{
case 'p': // Local port
if (strlen(argv[i]) > 3)
iPort = atoi(&argv[i][3]);
break;
case 'i': // Local IP addr
if (strlen(argv[i]) > 3)
; // You can add code here to handle the IP address if needed
break;
case 'b': // Buffer size
if (strlen(argv[i]) > 3)
dwLength = atol(&argv[i][3]);
break;
default:
usage();
break;
}
}
}
}
//
// Function: main
//
// Description:
// Main thread of execution. Initialize Winsock, parse the command
// line arguments, create a socket, bind to the local IP and port,
// and then receive datagram messages.
//
int main(int argc, char **argv)
{
WSADATA wsd;
SOCKET s;
char *recvbuf = NULL;
int ret;
SOCKADDR_IN local;
SOCKADDR_IN sender;
int senderSize;
// Parse the command line and load Winsock
ValidateArgs(argc, argv);
if (WSAStartup(MAKEWORD(2, 2), &wsd) != 0)
{
printf("WSAStartup failed!\n");
return 1;
}
// Create the socket
s = socket(AF_INET, SOCK_DGRAM, 0);
if (s == INVALID_SOCKET)
{
printf("socket() failed; %d\n", WSAGetLastError());
return 1;
}
// Bind to the local IP and port
local.sin_family = AF_INET;
local.sin_addr.s_addr = INADDR_ANY;
local.sin_port = htons((short)iPort);
if (bind(s, (SOCKADDR *)&local, sizeof(local)) == SOCKET_ERROR)
{
printf("bind() failed: %d\n", WSAGetLastError());
closesocket(s);
WSACleanup();
return 1;
}
// Allocate the receive buffer
recvbuf = (char *)malloc(dwLength);
if (!recvbuf)
{
printf("malloc() failed!\n");
closesocket(s);
WSACleanup();
return 1;
}
while (1)
{
senderSize = sizeof(sender);
// Receive data
ret = recvfrom(s, recvbuf, dwLength, 0, (SOCKADDR *)&sender, &senderSize);
if (ret == SOCKET_ERROR)
{
printf("recvfrom() failed; %d\n", WSAGetLastError());
break;
}
printf("Received %d bytes from %s:%d\n", ret, inet_ntoa(sender.sin_addr), ntohs(sender.sin_port));
// You can process the received data here
}
closesocket(s);
free(recvbuf);
WSACleanup();
return 0;
}