How to set up a Winsock UDP socket?
Please excuse the lack of error checking:
char pkt[...];
size_t pkt_length = ...;
sockaddr_in dest;
sockaddr_in local;
WSAData data;
WSAStartup( MAKEWORD( 2, 2 ), &data );
local.sin_family = AF_INET;
local.sin_addr.s_addr = inet_addr( <source IP address> );
local.sin_port = 0; // choose any
dest.sin_family = AF_INET;
dest.sin_addr.s_addr = inet_addr( <destination IP address> );
dest.sin_port = htons( <destination port number> );
// create the socket
SOCKET s = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
// bind to the local address
bind( s, (sockaddr *)&local, sizeof(local) );
// send the pkt
int ret = sendto( s, pkt, pkt_length, 0, (sockaddr *)&dest, sizeof(dest) );
The answer of Graeme Perrow doesn't work anymore because inet_addr is deprecated. Use inet_pton instead like this:
#include <string>
#include <WinSock2.h>
#include <Ws2tcpip.h>
#pragma comment(lib, "ws2_32.lib")
using namespace std;
int main() {
const char* pkt = "Message to be sent";
const char* srcIP = < source IP address >;
const char* destIP = < destination IP address >;
sockaddr_in dest;
sockaddr_in local;
WSAData data;
WSAStartup(MAKEWORD(2, 2), &data);
local.sin_family = AF_INET;
inet_pton(AF_INET, srcIP, &local.sin_addr.s_addr);
local.sin_port = htons(0);
dest.sin_family = AF_INET;
inet_pton(AF_INET, destIP, &dest.sin_addr.s_addr);
dest.sin_port = htons(< destination port number >);
SOCKET s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
bind(s, (sockaddr *)&local, sizeof(local));
sendto(s, pkt, strlen(pkt), 0, (sockaddr *)&dest, sizeof(dest));
closesocket(s);
WSACleanup();
return 0;
}