ampler/udp.c

// udp.c

/* TODO:
 * convert error codes to strings and print them, we could just make a table
 * option to change port, handle when we cant get gur port
 * be able to send packets when sounds / recording starts / ends ?

 * store from ip + port in message ?
*/

#include <winsock2.h>

#include "ampler.h"

// sadly, these mess with gur FD_SET macro ; - ;
#undef do
#undef if
#undef for
#undef while

// G l o b a L  E v i L //
static SOCKET udp_sock;

void udp_init(Ampler_state *state) {
	// https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsastartup
	WSADATA wsa;
	if (WSAStartup(MAKEWORD(2, 2), &wsa)) // we want version 2.2
		printf("error: WSAStartup() != 0, WSAGetLastError() = %i\n", WSAGetLastError());

	// https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-socket
	// SOCKET s = socket(
	udp_sock = socket(
		AF_INET, // ipv4
		SOCK_DGRAM, // udp
		0 // protocol, 0 = unspecified
	);
	if (udp_sock == INVALID_SOCKET)
		printf("error: socket is invalid, WSAGetLastError() = %i\n" , WSAGetLastError());

	// https://docs.microsoft.com/en-us/windows/win32/winsock/sockaddr-2
	struct sockaddr_in server; // sockaddr_in = ipv4
	const int PORT = 8888;
	server.sin_family = AF_INET; // ipv4
	server.sin_addr.s_addr = INADDR_ANY;
	server.sin_port = htons(PORT); // convert host to network byte order for short

	// https://docs.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-bind
	int bind_result = bind(
		udp_sock, // unbound socket, to be bound
		&server, // local address of socket
		sizeof(server) // sizeof address struct
	);
	if (bind_result == SOCKET_ERROR)
		printf("error: bind returned SOCKET_ERROR, WSAGetLastError() = %i\n" , WSAGetLastError());
}

void udp_quit(Ampler_state *state) {
	closesocket(udp_sock);
	WSACleanup();
}

void recv_packet(Ampler_state *state) {
	char discard_buf[32] = { 0 }; // for dropped packets
	char *buf = discard_buf;
	int buf_len = sizeof discard_buf;

	for (int i = 0; i < arraylen(state -> messages); i += 1) {
		Udp_msg *msg = &(state -> messages[i]);
		if (msg -> state == MSG_FREE) {
			msg -> state = MSG_TRIGGER;
			buf = msg -> text;
			buf_len = sizeof msg -> text;
			SDL_memset(buf, 0, buf_len);
			break;
		}
	}
	if (buf == discard_buf)
		puts("dropped udp packet.");

	struct sockaddr_in from_addr;
	int from_addr_size = sizeof from_addr;
	// https://docs.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-recvfrom
	int recv_len = recvfrom(
		udp_sock, // socket to recive on
		buf, // buffer for recv'd data
		buf_len - 1, // size of buffer in bytes, '- 1' preserves null terminator
		0, // flags
		&from_addr, // address struct to recieve source of packet
		&from_addr_size // POINTER to size of address struct
	);
	if (recv_len == SOCKET_ERROR)
		if (WSAGetLastError() != WSAEMSGSIZE) // packet was truncated to fit buffer
			printf("error: recvfrom returned SOCKET_ERROR, WSAGetLastError() = %i\n" , WSAGetLastError());

	// convert to ipv4 address string, stored in static buffer, next call overwrites
	const char *from_ip_str = inet_ntoa(from_addr.sin_addr);
	int from_port = ntohs(from_addr.sin_port); // convert network to host byte order for short
	if (0) // FOR DEBUGGING
		printf("%s:%d\t%s\n", from_ip_str, from_port, buf);
}

void udp_frame(Ampler_state *state) {
	// https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-select
	fd_set recv_fd_set;
	FD_ZERO(&recv_fd_set); // init / clear set

	// https://docs.microsoft.com/en-us/windows/win32/api/winsock/ns-winsock-timeval
	TIMEVAL timeout;
	timeout.tv_sec = 0;
	timeout.tv_usec = 1000; // 1 ms

	while (1) {
		// https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-select
		FD_SET(udp_sock, &recv_fd_set); // add server socket to set
		int can_recv = select( // returns gur number of sockets, we can recv on, 0 on timeout
			0, // ignored on win, used for compatability
			&recv_fd_set, // soc set to be checked for reading
			NULL, // set to be checked for writing
			NULL, // set to be checked for errors
			&timeout // max time to wait for
		);
		if (can_recv == SOCKET_ERROR)
			printf("error: select returned SOCKET_ERROR, WSAGetLastError() = %i\n", WSAGetLastError());

		if (FD_ISSET(udp_sock, &recv_fd_set)) {
			// puts("soc in set, we can recv data!");
		}
		else {
			// puts("timeout");
			return;
		}
		
		recv_packet(state);
	}
}