echo_dgram_client_winsock2.c

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <WinSock2.h>
#include <stdlib.h>
#include <stdio.h>

int main(int argc, char *argv[]) {
	WSADATA wsaData = { 0 };
	WSAStartup(MAKEWORD(2, 2), &wsaData);

	SOCKET sock = socket(AF_INET, SOCK_DGRAM, 0);
	if (sock == INVALID_SOCKET) {
		return EXIT_FAILURE;
	}

	if (argc != 4) {
		printf("Usage: echo_dgram_client ip port message\n");
		return EXIT_FAILURE;
	}

	unsigned ip = inet_addr(argv[1]);
	unsigned port = atoi(argv[2]);
	const char *message = argv[3];

	struct sockaddr_in sa;
	sa.sin_family = AF_INET;
	sa.sin_port = htons(port);
	sa.sin_addr.s_addr = ip;

	int bytes_sent = sendto(sock, message, strlen(message), 0, (const struct sockaddr*)&sa, sizeof(sa));
	if (bytes_sent == -1) {
		fprintf(stderr, "sendto failed!\n");
		return EXIT_FAILURE;
	}

	return EXIT_SUCCESS;
}