network_udp.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#include "../stdafx.h"
 
#include "../debug.h"
#include "network_internal.h"
#include "network_udp.h"
 
#include "core/udp.h"
 
#include "../safeguards.h"
 
static bool _network_udp_server;         
static uint16_t _network_udp_broadcast;    

struct UDPSocket {
  const std::string name;                     
  std::unique_ptr<NetworkUDPSocketHandler> socket = nullptr; 
 
  UDPSocket(const std::string &name) : name(name) {}
 
  void CloseSocket()
  {
    this->socket->CloseSocket();
    this->socket = nullptr;
  }
 
  void ReceivePackets()
  {
    this->socket->ReceivePackets();
  }
};
 
static UDPSocket _udp_client("Client"); 
static UDPSocket _udp_server("Server"); 
 
/* Communication with clients (we are server) */

class ServerNetworkUDPSocketHandler : public NetworkUDPSocketHandler {
protected:
  void Receive_CLIENT_FIND_SERVER(Packet &p, NetworkAddress &client_addr) override;
public:
  ServerNetworkUDPSocketHandler(NetworkAddressList *addresses) : NetworkUDPSocketHandler(addresses) {}
  ~ServerNetworkUDPSocketHandler() override = default;
};
 
void ServerNetworkUDPSocketHandler::Receive_CLIENT_FIND_SERVER(Packet &, NetworkAddress &client_addr)
{
  Packet packet(this, PACKET_UDP_SERVER_RESPONSE);
  this->SendPacket(packet, client_addr);
 
  Debug(net, 7, "Queried from {}", client_addr.GetHostname());
}
 
/* Communication with servers (we are client) */

class ClientNetworkUDPSocketHandler : public NetworkUDPSocketHandler {
protected:
  void Receive_SERVER_RESPONSE(Packet &p, NetworkAddress &client_addr) override;
public:
  ~ClientNetworkUDPSocketHandler() override = default;
};
 
void ClientNetworkUDPSocketHandler::Receive_SERVER_RESPONSE(Packet &, NetworkAddress &client_addr)
{
  Debug(net, 3, "Server response from {}", client_addr.GetAddressAsString());
 
  NetworkAddServer(client_addr.GetAddressAsString(false), false, true);
}

static void NetworkUDPBroadCast(NetworkUDPSocketHandler &socket)
{
  for (NetworkAddress &addr : _broadcast_list) {
    Debug(net, 5, "Broadcasting to {}", addr.GetHostname());
 
    Packet p(&socket, PACKET_UDP_CLIENT_FIND_SERVER);
    socket.SendPacket(p, addr, true, true);
  }
}

void NetworkUDPSearchGame()
{
  /* We are still searching.. */
  if (_network_udp_broadcast > 0) return;
 
  Debug(net, 3, "Searching server");
 
  NetworkUDPBroadCast(*_udp_client.socket);
  _network_udp_broadcast = 300; // Stay searching for 300 ticks
}

void NetworkUDPInitialize()
{
  /* If not closed, then do it. */
  if (_udp_server.socket != nullptr) NetworkUDPClose();
 
  Debug(net, 3, "Initializing UDP listeners");
  assert(_udp_client.socket == nullptr && _udp_server.socket == nullptr);
 
  _udp_client.socket = std::make_unique<ClientNetworkUDPSocketHandler>();
 
  NetworkAddressList server;
  GetBindAddresses(&server, _settings_client.network.server_port);
  _udp_server.socket = std::make_unique<ServerNetworkUDPSocketHandler>(&server);
 
  _network_udp_server = false;
  _network_udp_broadcast = 0;
}

void NetworkUDPServerListen()
{
  _network_udp_server = _udp_server.socket->Listen();
}

void NetworkUDPClose()
{
  _udp_client.CloseSocket();
  _udp_server.CloseSocket();
 
  _network_udp_server = false;
  _network_udp_broadcast = 0;
  Debug(net, 5, "Closed UDP listeners");
}

void NetworkBackgroundUDPLoop()
{
  if (_network_udp_server) {
    _udp_server.ReceivePackets();
  } else {
    _udp_client.ReceivePackets();
    if (_network_udp_broadcast > 0) _network_udp_broadcast--;
  }
}