feat: Implement multiplayer functionality.

- Server can handle multiple clients simultaneously.
- Client can see other players in the game.
- Server broadcasts the game state to all clients.
- Client receives the game state and renders the other players.
- Server assigns a unique ID to each player.
- Client receives its player ID form the server.
- Server handles client disconnections.. Kinda... Server is ignoring
  SIGPIPE signal.
- Server and client signals are non-blocking.
- Moved player objects off the stack and onto the heap.

libbettola/include/bettola/network/message.h

@@ -7,6 +7,7 @@ enum class MessageType : unsigned char {
   PlayerPosition,
   PlayerState,
   GameState,
+  PlayerId,
 };
 
 struct MessageHeader {

libbettola/src/bettola/network/socket.cpp

@@ -5,6 +5,7 @@
 #include <sys/socket.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <cerrno>
 
 #include "bettola/network/socket.h"
 #include "bettola/network/net_common.h"
@@ -34,11 +35,6 @@ bool Socket::create(void) {
     perror("fcntl F_GETFL failed.");
     return false;
   }
-  if(fcntl(_sockfd, F_SETFL, flags & ~O_NONBLOCK) == -1) {
-    perror("fcntl F_SETFL O_NONBLOCK failed");
-    return false;
-  }
-
   return true;
 }
 
@@ -74,7 +70,8 @@ Socket* Socket::accept(void) {
   socklen_t client_len = sizeof(client_addr);
   int client_sockfd = ::accept(_sockfd, (struct sockaddr*)&client_addr, &client_len);
   if(client_sockfd == -1) {
-    perror("Socket accept failed.");
+    if(errno != EWOULDBLOCK && errno != EAGAIN)
+      perror("Socket accept failed.");
     return nullptr;
   }
 
@@ -97,7 +94,7 @@ bool Socket::connect(const std::string& ip_address, unsigned short port) {
     return false;
   }
 
-  if(::connect(_sockfd, (struct sockaddr*)&_address, sizeof(_address)) == -1) {
+  if(::connect(_sockfd, (struct sockaddr*)&_address, sizeof(_address)) < 0) {
     fprintf(stderr, "Socket::connect() failed for sockfd %d with errno %d: %s\n", _sockfd,
             errno, strerror(errno));
     perror("Connection failed.");
@@ -117,7 +114,7 @@ ssize_t Socket::send(const void* buffer, size_t length) {
 
 ssize_t Socket::recv(void* buffer, size_t length) {
   ssize_t bytes_received = ::recv(_sockfd, buffer, length, 0);
-  if(bytes_received == -1) {
+  if(bytes_received == -1 && errno != EWOULDBLOCK && errno != EAGAIN) {
     perror("Receive failed.");
   }
   return bytes_received;

src/bettola.cpp

@@ -1,17 +1,22 @@
 #include <GL/glew.h>
 #include <SDL3/SDL_error.h>
+#include <algorithm>
 /* FINE LSP!! I'll play your games!!!! */
 #include <SDL3/SDL_events.h> /* ~HJAPPY?!?!?! */
 #include <SDL3/SDL_stdinc.h>
 #include <SDL3/SDL_timer.h>
 #include <SDL3/SDL_video.h>
+#include <fcntl.h>
+#include <cstddef>
 #include <cstdio>
 #include <string>
 
 #include "bettola.h"
 #include "bettola/network/socket.h"
 #include "bettola/network/net_common.h"
+#include "math/mat4.h"
 #include "network/message.h"
+#include "network/game_state_message.h"
 #include "network/player_pos_message.h"
 
 /* Dacav's resolution ;) */
@@ -23,7 +28,8 @@ Bettola::Bettola(void) :
     _window(nullptr),
     _gl_context(nullptr),
     _vao(0),
-    _vbo(0) {}
+    _vbo(0),
+    _our_player_id(0) {}
 
 Bettola::~Bettola(void) {
   if(_gl_context) {
@@ -97,6 +103,28 @@ int Bettola::run(void) {
       network_time = 0.0;
     }
 
+    if(_our_player_id == 0) {
+      BettolaLib::Network::MessageHeader id_header;
+      ssize_t id_bytes_received = _client_socket.recv(&id_header, sizeof(id_header));
+      if(id_bytes_received > 0 && id_header.type == BettolaLib::Network::MessageType::PlayerId) {
+        _client_socket.recv(&_our_player_id, sizeof(_our_player_id));
+      }
+    }
+
+    while(true) {
+      BettolaLib::Network::MessageHeader header;
+      ssize_t bytes_received = _client_socket.recv(&header, sizeof(header));
+      if(bytes_received <= 0) {
+        break;
+      }
+      if(header.type == BettolaLib::Network::MessageType::GameState) {
+        BettolaLib::Network::GameStateMessage msg;
+        if(_client_socket.recv(&msg, sizeof(msg)) > 0) {
+          update_remote_players(msg);
+        }
+      }
+    }
+
     process_events();
     update(delta_time);
     render();
@@ -171,9 +199,50 @@ void Bettola::render(void) {
   glDrawArrays(GL_TRIANGLES, 0, 6);
   glBindVertexArray(0);
 
+  /* Render remote players. */
+  for(const auto& remote_player : _remote_players) {
+    BettolaMath::Mat4 remote_trans_matrix =
+      BettolaMath::Mat4::translation(remote_player.get_x(),
+                                     remote_player.get_y(),
+                                     0.0f);
+
+    BettolaMath::Mat4 remote_scale_matrix =
+      /* Assuming remote players have same size as local player. */
+      BettolaMath::Mat4::scale(50.0f, 50.0f, 1.0f);
+
+    BettolaMath::Mat4 remote_model = remote_trans_matrix.multiply(remote_scale_matrix);
+
+    glUniformMatrix4fv(model_loc, 1, GL_FALSE, remote_model.get_ptr());
+
+    glBindVertexArray(_vao);
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    glBindVertexArray(0);
+  }
+
   SDL_GL_SwapWindow(_window);
 }
 
+void Bettola::update_remote_players(const BettolaLib::Network::GameStateMessage& msg) {
+  for(unsigned int i = 0; i < msg.num_players; ++i) {
+    const auto& player_state = msg.players[i];
+
+    auto it = std::find_if(_remote_players.begin(), _remote_players.end(),
+                           [player_state](const RemotePlayer& remote_player) {
+                              return remote_player.get_id() == player_state.player_id;
+                           });
+
+    if(it != _remote_players.end()) {
+      it->set_position(player_state.x, player_state.y);
+    } else {
+      /* We don't want to add ourselves as a remote player! */
+      if(player_state.player_id != _our_player_id) {
+        _remote_players.emplace_back(player_state.player_id, player_state.x,
+                                     player_state.y);
+      }
+    }
+  }
+}
+
 bool Bettola::init_sdl(void) {
   if(!SDL_Init(SDL_INIT_VIDEO)) {
     fprintf(stderr, "Failed to iniit SDL! SDL ERROR: %s\n", SDL_GetError());
@@ -257,6 +326,14 @@ bool Bettola::init_client_connection(void) {
     return false;
   }
 
+  /* Set the socket to non-blocking. */
+  int flags = fcntl(_client_socket.get_sockfd(), F_GETFL, 0);
+  if(flags == -1) {
+    perror("fcntl F_GETFL failed.");
+    return false;
+  }
+  fcntl(_client_socket.get_sockfd(), F_SETFL, flags | O_NONBLOCK);
+
   printf("Bettola Client: Connected to server at 127.0.01.:%hu\n", BettolaLib::Network::DEFAULT_PORT);
   return true;
 }

src/bettola.h

@@ -1,11 +1,14 @@
 #pragma once
 
 #include <SDL3/SDL.h>
+#include <vector>
 
 #include "graphics/shader.h"
 #include "game/player.h"
+#include "game/remote_player.h"
 #include "math/mat4.h"
 #include "bettola/network/socket.h"
+#include "network/game_state_message.h"
 
 class Bettola {
 public:
@@ -18,6 +21,7 @@ private:
   void process_events(void);
   void update(double dt);
   void render(void);
+  void update_remote_players(const BettolaLib::Network::GameStateMessage& msg);
 
   bool init_sdl(void);
   bool init_glew(void);
@@ -37,6 +41,7 @@ private:
 
   bool _is_running;
 
+  unsigned int  _our_player_id;
   SDL_Window*   _window;
   SDL_GLContext _gl_context;
 
@@ -47,5 +52,6 @@ private:
   BettolaMath::Mat4 _projection;
   Player _player;
   InputState _input;
+  std::vector<RemotePlayer> _remote_players;
   BettolaLib::Network::Socket _client_socket;
 };

src/game/remote_player.cpp

@@ -0,0 +1,8 @@
+#include "remote_player.h"
+
+RemotePlayer::RemotePlayer(unsigned int id, float x, float y) :
+    _id(id), _x(x), _y(y) {}
+
+void RemotePlayer::set_position(float x, float y) {
+  _x = x; _y = y;
+}

src/game/remote_player.h

@@ -0,0 +1,17 @@
+#pragma once
+
+class RemotePlayer {
+public:
+  RemotePlayer(unsigned int id, float x, float y);
+
+  void set_position(float x, float y);
+
+  unsigned int get_id(void) const { return _id; }
+  float get_x(void) const { return _x; }
+  float get_y(void) const { return _y; }
+
+private:
+  unsigned int _id;
+  float _x;
+  float _y;
+};

srv/game/game.cpp

@@ -6,27 +6,26 @@
 #include "network/message.h"
 
 Player* Game::add_player(BettolaLib::Network::Socket* socket) {
-  _players.emplace_back(socket);
-  return &_players.back();
+  _players.push_back(new Player(socket));
+  return _players.back();
 }
 
 void Game::remove_player(unsigned int player_id) {
   _players.erase(
     std::remove_if(_players.begin(), _players.end(),
-                   [player_id](const Player& player) {
-                      /* this is a sh.t way to compare players. */
-                      return player.get_id() == player_id;
+                   [player_id](const Player* player) {
+                      return player->get_id() == player_id;
                    }),
     _players.end());
 }
 
 void Game::update_player_pos(unsigned int player_id, float x, float y) {
   auto it = std::find_if(_players.begin(), _players.end(),
-                         [player_id](const Player& player) {
-                            return player.get_id() == player_id;
+                         [player_id](const Player* player) {
+                            return player->get_id() == player_id;
                          });
   if(it != _players.end()) {
-    it->set_position(x, y);
+    (*it)->set_position(x, y);
   }
 }
 
@@ -35,9 +34,9 @@ void Game::broadcast_game_state(void) {
   msg.num_players = _players.size();
 
   for(size_t i = 0; i < _players.size(); ++i) {
-    msg.players[i].player_id = _players[i].get_id();
-    msg.players[i].x = _players[i].get_x();
-    msg.players[i].y = _players[i].get_y();
+    msg.players[i].player_id = _players[i]->get_id();
+    msg.players[i].x = _players[i]->get_x();
+    msg.players[i].y = _players[i]->get_y();
   }
 
   BettolaLib::Network::MessageHeader header;
@@ -45,9 +44,23 @@ void Game::broadcast_game_state(void) {
   header.size = sizeof(msg);
 
   for(const auto& player : _players) {
-    BettolaLib::Network::Socket& socket = player.get_socket();
-    socket.send(&header, sizeof(header));
-    socket.send(&msg, sizeof(msg));
+    BettolaLib::Network::Socket& socket = player->get_socket();
+    /* Just quick fix the server crash for now. */
+    if(socket.send(&header, sizeof(header)) <= 0) {
+      /* TODO: Probably should handle this error by removing player.. */
+    }
+    if(socket.send(&msg, sizeof(msg)) <= 0) {
+      /* TODO: Probably should handle this error by removing player.. */
+    }
   }
 }
 
+Player* Game::get_player_by_socket(BettolaLib::Network::Socket* socket) {
+  auto it = std::find_if(_players.begin(), _players.end(),
+                         [socket](const Player* player) {
+                            return &player->get_socket() == socket;
+                         });
+
+  return(it != _players.end() ? *it : nullptr);
+}
+

srv/game/game.h

@@ -10,7 +10,8 @@ public:
   void remove_player(unsigned int player_id);
   void update_player_pos(unsigned int player_id, float x, float y);
   void broadcast_game_state(void);
+  Player* get_player_by_socket(BettolaLib::Network::Socket* socket);
 
 private:
-  std::vector<Player> _players;
+  std::vector<Player*> _players;
 };

srv/main.cpp

@@ -2,6 +2,9 @@
 #include <cstdio>
 #include <chrono>
 #include <thread>
+#include <vector>
+#include <fcntl.h>
+#include <signal.h>
 
 #include "bettola/network/socket.h"
 #include "bettola/network/net_common.h"
@@ -11,6 +14,9 @@
 
 int main(void) {
   Game game;
+  std::vector<BettolaLib::Network::Socket*> client_sockets;
+
+  signal(SIGPIPE, SIG_IGN);
 
   printf("=== Bettola Server: Starting ===\n");
 
@@ -36,46 +42,81 @@ int main(void) {
 
   printf("Bettola Server: Listening on port %hu...\n", BettolaLib::Network::DEFAULT_PORT);
 
+  /* Set the server socket to non-blocking. */
+  int flags = fcntl(server_socket.get_sockfd(), F_GETFL, 0);
+  if(flags == -1) {
+    perror("fcntl F_GETFL, failed.");
+    return 1;
+  }
+  fcntl(server_socket.get_sockfd(), F_SETFL, flags | O_NONBLOCK);
+
   auto last_time = std::chrono::high_resolution_clock::now();
 
   /* Main server loop. */
   while(true) {
-    auto current_time = std::chrono::high_resolution_clock::now();
-    auto delta_time = std::chrono::duration_cast<std::chrono::duration<double>>
-      (current_time-last_time).count();
-
-    /* TODO:
-     * Accept new connections.
-     * This is blocking.. Will fix later.
-     */
+    /* Accept new connections. */
     BettolaLib::Network::Socket* client_socket = server_socket.accept();
     if(client_socket != nullptr) {
       Player* new_player = game.add_player(client_socket);
       printf("Bettola Server: Client connected! Player ID: %u\n", new_player->get_id());
+
+      BettolaLib::Network::MessageHeader header;
+      header.type = BettolaLib::Network::MessageType::PlayerId;
+      header.size = sizeof(unsigned int);
+      client_socket->send(&header, sizeof(header));
+      unsigned int id = new_player->get_id();
+      client_socket->send(&id, sizeof(id));
+
+      /* Set the client socket to non-blocking. */
+      int client_flags = fcntl(client_socket->get_sockfd(), F_GETFL, 0);
+      if(client_flags == -1) {
+        perror("fcntl F_GETFL failed");
+        return 1;
+      }
+      fcntl(client_socket->get_sockfd(), F_SETFL, client_flags | O_NONBLOCK);
+
+      client_sockets.push_back(client_socket);
     }
 
-    /* TODO:
-     * Process messages from clients.
-     * this is also blocking and only handles one client at a time. fix later
-     */
-    if(client_socket != nullptr) {
+    /* Process messages from clients. */
+    for(auto it = client_sockets.begin(); it != client_sockets.end();) {
+      BettolaLib::Network::Socket* client = *it;
+      bool client_disconnected = false;
+
       while(true) {
         BettolaLib::Network::MessageHeader header;
-        ssize_t bytes_received = client_socket->recv(&header, sizeof(header));
+        /* Non-blocking. */
+        ssize_t bytes_received = client->recv(&header, sizeof(header));
 
-        if(bytes_received <= 0) {
-          //game.remove_player(new_player->get_id());
+        if(bytes_received == 0) {
+          client_disconnected = true;
+          break;
+        }
+
+        if(bytes_received < 0) {
+          /* No data to read.. */
           break;
         }
 
         if(header.type == BettolaLib::Network::MessageType::PlayerPosition) {
           BettolaLib::Network::PlayerPosMessage msg;
-          bytes_received = client_socket->recv(&msg, sizeof(msg));
+          bytes_received = client->recv(&msg, sizeof(msg));
           if(bytes_received > 0) {
-            //game.update_player_pos(new_player->get_id(), msg.x, msg.y);
+            Player* player = game.get_player_by_socket(client);
+            if(player) {
+              game.update_player_pos(player->get_id(), msg.x, msg.y);
+            }
           }
         }
       }
+
+      if(client_disconnected) {
+        Player* player = game.get_player_by_socket(client);
+        if(player) game.remove_player(player->get_id());
+        it = client_sockets.erase(it);
+      } else {
+        ++it;
+      }
     }
 
     /* Broadcase game state. */