SanAndreasUnity/Assets/Scripts/Behaviours/MasterServerClient.cs

using System;
using Newtonsoft.Json;
using SanAndreasUnity.Net;
using SanAndreasUnity.Utilities;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using UnityEngine;

public class MasterServerClient : MonoBehaviour
{
    private string _masterServerUrl;
    private ServerInfo _serverInfo;
    private bool _updating;
    public static MasterServerClient Instance { get; private set; }
    private HttpClient _client;


    private void Awake()
    {
        Instance = this;
    }

    private void Start()
    {
        _client = new HttpClient();

        Config.Load();
        _masterServerUrl = Config.Get<string>("masterserverurl");

        if (string.IsNullOrWhiteSpace(_masterServerUrl))
            Debug.LogError("Url of master server not defined in config");

        NetManager.Instance.onServerStatusChanged += OnServerStatusChange;
    }

    private async void OnServerStatusChange()
    {
        if (!NetStatus.IsServer)
            return;

        if (string.IsNullOrWhiteSpace(_masterServerUrl))
            return;

        _serverInfo = new ServerInfo
        {
            Name = Config.Get<string>("server_name"),
            Port = NetManager.listenPortNumber,
            NumPlayersOnline = NetManager.numConnections,
            MaxPlayers = NetManager.maxNumPlayers,
        };

        await RegisterServer();
    }

    private async Task RegisterServer()
    {
        await SendRequestToRegister();

        _updating = true;
        Invoke(nameof(UpdateServer), 10);
    }

    private async Task UpdateServer()
    {
        while (_updating)
        {
            _serverInfo.NumPlayersOnline = NetManager.numConnections;

            await SendRequestToRegister();

            await Task.Delay(10000);
        }
    }

    private async Task SendRequestToRegister()
    {
        var response = await _client.PostAsync(_masterServerUrl + "/register", new StringContent(JsonConvert.SerializeObject(_serverInfo), Encoding.UTF8, "application/json"));

        if (!response.IsSuccessStatusCode)
        {
            string str = await response.Content.ReadAsStringAsync();
            Debug.LogError($"Master server returned error while trying to register: {str}");
        }
    }

    private async Task UnregisterServer()
    {
        _updating = false;

        if (null == _serverInfo)
            return;

        if (string.IsNullOrWhiteSpace(_masterServerUrl))
            return;

        await _client.PostAsync(_masterServerUrl + "/unregister", new StringContent(JsonConvert.SerializeObject(_serverInfo), Encoding.UTF8, "application/json"));
    }

    public async Task<List<ServerInfo>> GetAllServers()
    {
        if (string.IsNullOrWhiteSpace(_masterServerUrl))
            return new List<ServerInfo>();

        return JsonConvert.DeserializeObject<List<ServerInfo>>(await _client.GetStringAsync(_masterServerUrl));
    }

    public async void OnDestroy()
    {
        await UnregisterServer();
    }
}

public class ServerInfo
{
    public string Name { get; set; }
    public int NumPlayersOnline { get; set; }
    public string IP { get; set; }
    public int Port { get; set; }
    public int MaxPlayers { get; set; }
}