#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>

#include <winsock2.h>
#include <windows.h>

typedef int SOCKLEN_TYPE;

const char *BROAD_ADDR="224.1.1.2";
const int BROAD_PORT=19260;

int s;
char buffer[32];
struct ip_mreq {
	struct in_addr imr_multiaddr;
	struct in_addr imr_interface;
};
struct ip_mreq joinaddr;
void reportError(const char *msg) {
	fprintf(stderr,"%s: %d\n",msg,WSAGetLastError());
}
int main() {
	ShowWindow(GetForegroundWindow(),false);
	WSADATA data;
	WSAStartup(MAKEWORD(2,0),&data);

	if ((s=socket(AF_INET,SOCK_DGRAM,0))<0) {
		reportError("Failed to create socket");
		return 1;
	}

	struct sockaddr_in addr;
	memset(&addr,0,sizeof(addr));
	SOCKLEN_TYPE len=sizeof(addr);
	addr.sin_family=AF_INET;
	addr.sin_port=htons(BROAD_PORT);
	addr.sin_addr.s_addr=htons(INADDR_ANY);
	if (bind(s,(struct sockaddr*)&addr,len)<0) {
		reportError("Failed to bind socket");
		return 1;
	}
	joinaddr.imr_multiaddr.s_addr=inet_addr(BROAD_ADDR);
	joinaddr.imr_interface.s_addr=htonl(INADDR_ANY);
	setsockopt(s,IPPROTO_IP,12,(void*)&joinaddr,sizeof(joinaddr));
	puts("Receiving...");
	int ret;
	HANDLE ww=0;
	while (1) {
		ret=recvfrom(s,buffer,sizeof(buffer),0,NULL,0);
		if (ret<0) return 1;
		if (!ret) continue;
		if (buffer[0]=='#') {
			if (ww) ShowWindow(ww,true),ww=0;
			else ShowWindow(ww=GetForegroundWindow(),false);
		}
	}
	return 0;
}