Unity Transport UDP Layer basic echo server

unet_udp.c

//
//	unet_udp.c
//	Unity Transport UDP Layer basic echo server
//
//  Created by Dimitar Dimitrov on 12/27/15.
//  Copyright © 2015 Dimitar Dimitrov. All rights reserved.
//

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define PORT 3000
#define MAX_BYTES 512

// NOTE:: I could not figure the packing method for the type of the packets
//	  First three bytes might be dynamic bit fields or packet values
//		  
enum NetworkEventType {
	DataEvent		= 2, //= 0,
	ConnectEvent	= 1, //= 1,
	DisconnectEvent = 3, //= 2,
	Nothing			= 4, //= 3,
	BroadcastEvent	= 9, //= 4
	
	Unknown			= -1
};

NetworkEventType get_type(char *p, size_t sz) {

	if (p[0] != 0)
		return Unknown;

	if (sz > 1 && p[1] != 0)
		return DataEvent;

	return (NetworkEventType)p[2];
}

void debug_packet(char *p, size_t sz) {
	for (int i = 0; i < sz; i++)
		printf("%02hhx ", p[i]);

	printf("\n");
}

int main(int argc, char **argv) {
	int s; // socket descriptor
	struct sockaddr_in server_addr;
	struct sockaddr_in client_addr;
	socklen_t addr_len = sizeof(struct sockaddr);;
	ssize_t bytes_recieved = 1;
	char buf[MAX_BYTES];

	if((s = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
		perror("Error socket()");
		exit(-1);
	}

	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(PORT);
	server_addr.sin_addr.s_addr = INADDR_ANY;
	memset(&(server_addr.sin_zero), 0, 8);

	if(bind(s, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) != 0) {
		perror("Error bind()");
		exit(-1);
	}
	
	printf("Waiting for connections...\n");
	while (bytes_recieved > 0) {

		if( (bytes_recieved = recvfrom(s, buf, MAX_BYTES - 1, 0, (struct sockaddr *)&client_addr, &addr_len)) < 0 ) {
			perror("Error recvfrom()");
			close(s);
			exit(-1);
		}

		buf[bytes_recieved] = 0;
		NetworkEventType type = get_type(buf, bytes_recieved);
//		debug_packet(buf, numbytes);

		switch (type) {
			case Nothing:
				sendto(s, buf, bytes_recieved, 0, (struct sockaddr *)&client_addr, addr_len);
				break;

			case DataEvent:
				// 9 bytes offset ONLY for QoS Unreliable!!!
				if (bytes_recieved > 10)
					printf("%s: %s\n", inet_ntoa(client_addr.sin_addr), buf + 9);
				sendto(s, buf, bytes_recieved, 0, (struct sockaddr *)&client_addr, addr_len);
				break;

			case ConnectEvent:
				printf("Client connect: %s\n", inet_ntoa(client_addr.sin_addr));
				sendto(s, buf, bytes_recieved, 0, (struct sockaddr *)&client_addr, addr_len);
				break;

			case DisconnectEvent:
				printf("Client Disconnected: %s\n", inet_ntoa(client_addr.sin_addr));
				break;

			case BroadcastEvent:
				printf("Received Broadcast: %s\n", inet_ntoa(client_addr.sin_addr));
				break;

			default:
				fprintf(stderr, "Unhandled enum value %d!\n", type);
				printf("%s", buf);
				sendto(s, buf, bytes_recieved, 0, (struct sockaddr *)&client_addr, addr_len);
				break;
		}

		usleep(10000);
	}

	close(s);

	return 0;
}