Basic data retrieval from X-Plane using winsock2 over UDP

XPlaneIntf.c

// XPlaneC.cpp : Defines the entry point for the console application.

// References
// http://www.nuclearprojects.com/xplane/xplaneref.html
// http://www.nuclearprojects.com/xplane/info.shtml
// https://docs.microsoft.com/en-us/windows/desktop/winsock/windows-sockets-error-codes-2
// https://stackoverflow.com/questions/32471004/udp-client-not-receiving-udp-server-message

#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include <windows.h>      // Needed for all Winsock stuff

#pragma comment(lib,"ws2_32.lib") //Winsock Library

//----- Defines ---------------------------------------------------------------
#define  PORT_NUM           49003  // Port number used
#define  IP_ADDR      "127.0.0.1" // IP address of server1 (*** HARDWIRED ***)

#define XCHR char		// (character, in local byte - order for the machine you are on)
#define XINT int		// (4 - byte int, in local byte - order for the machine you are on)
#define XFLT float		// (4 - byte ints and floats, in local byte - order for the machine you are on)
#define XDOB double		// (double - precision float, in local byte - order for the machine you are on)
#define strDIM 500
#define vehDIM 10
#define net_SIZE_buff 1024

typedef enum state { 
	LAT_LON_ALT = 20
} State;

typedef struct lat_lon_alt_type {
	float lat_deg;
	float lon_deg;
	float alt_ftmsl;
	float alt_ftagl;
	float on_runway;
	float alt_ind;
	float lat_orign;
	float lon_orign;
} lat_lon_alt_type;

struct data_struct
{
	int index; // data index, the index into the list of variables you can output from the Data Output screen in X-Plane.
	float data[8]; // the up to 8 numbers you see in the data output screen associated with that selection.. many outputs do not use all 8, though.
};

void NET_send(int client, sockaddr_in server_addr, XCHR label[5], XCHR* data_in, XINT data_len)
{
	XCHR				data_send[net_SIZE_buff];
	
	data_send[0] = label[0];
	data_send[1] = label[1];
	data_send[2] = label[2];
	data_send[3] = label[3];
	data_send[4] = 0;
	memcpy(&data_send[5], data_in, data_len);	// load in the data
	data_len += 5;

	XINT send_failed = (sendto(client, data_send, data_len, 0, (const struct sockaddr*)&server_addr, sizeof(struct sockaddr_in)) != data_len);
	if (send_failed < 0)
	{
		int err = WSAGetLastError();
		printf("sendto() failed with error code : %d\n", err);
		exit(-1);
	}
}

void NET_recv(int client, sockaddr_in server_addr, XCHR *label, data_struct *data)
{
	XCHR data_out[net_SIZE_buff];
	int addr_len = sizeof(server_addr);
	int retcode = recvfrom(client, data_out, net_SIZE_buff, 0, (struct sockaddr *)&server_addr, &addr_len);
	if (retcode < 0)
	{
		int err = WSAGetLastError();
		printf("recvfrom() failed with error code : %d\n", err);
		exit(-1);
	}
	if (strncmp(data_out, "DATA", 4) == 0)
	{
		memcpy(data, data_out + 5, sizeof(data_struct));
	}
}

int setup_socket(int *client_s, sockaddr_in *server_addr)
{
	int opt = 1;

	*client_s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (client_s < 0)
	{
		printf("*** ERROR - socket() failed \n");
	}

	//UDP Broadcast permissions
	if (setsockopt(*client_s, SOL_SOCKET, SO_BROADCAST, (char *)&opt, sizeof(opt)) == SOCKET_ERROR)
	{
		printf("\nERROR in broadcasting ERROR CODE : %d \n", WSAGetLastError());
		closesocket(*client_s);
		WSACleanup();
		return 1;
	}

	//UDP SOCKET Binding 
	if (bind(*client_s, (sockaddr *)server_addr, sizeof(sockaddr_in)) == SOCKET_ERROR)
	{
		int err = WSAGetLastError();
		printf("\nUDP socket binding failed ERROR CODE : %d\n", err);
		closesocket(*client_s);
		WSACleanup();
		exit(-1);
	}
}

//===== Main program ==========================================================
int main()
{
	WORD wVersionRequested = MAKEWORD(1, 1);       // Stuff for WSA functions
	WSADATA wsaData;                              // Stuff for WSA functions
	int client_s;
	sockaddr_in server_addr;

	WSAStartup(wVersionRequested, &wsaData);
	server_addr.sin_family = AF_INET;                 // Address family to use
	server_addr.sin_port = htons(PORT_NUM);           // Port num to use
	server_addr.sin_addr.s_addr = INADDR_ANY;

	setup_socket(&client_s, &server_addr);

	for (;;)
	{
		char label[5];
		data_struct d;
		NET_recv(client_s, server_addr, label, &d);

		//printf("Index: %d\n", d.index);
		//for (int j = 0; j < 8; j++)
		//{
		//	printf("d[%d] = %.2f\n ", j, d.data[j]);
		//}
		//printf("\n");

		switch(d.index)
		{
			case LAT_LON_ALT:
				lat_lon_alt_type *t = (lat_lon_alt_type*) d.data;
				printf("Lat: %f\n", t->lat_deg);
				printf("Lon: %f\n", t->lon_deg);
				printf("Alt MSL: %f\n", t->alt_ftmsl);
				printf("ALt AGL: %f\n", t->alt_ftagl);
				printf("Alt Ind: %f\n", t->alt_ind);
				printf("On rwy: %f\n", t->on_runway);
				printf("Lat Orign: %f\n", t->lat_orign);
				printf("Lon Orign: %f\n", t->lon_orign);
				break;
		}
		printf("\n");

		Sleep(100);
	}

	if (closesocket(client_s) < 0)
	{
		printf("*** ERROR - closesocket() failed \n");
		exit(-1);
	}

	WSACleanup();
	return(0);
}