TcpServer.java

/* Copyright (c) 2011 Danish Maritime Authority.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package dk.dma.ais.bus.tcp;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Collections;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicReference;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import dk.dma.ais.bus.AisBusComponent;

/**
 * Base class for TCP servers. Spawns and handles TCP clients.
 */
public abstract class TcpServer extends Thread implements IClientStoppedListener {

    private static final Logger LOG = LoggerFactory.getLogger(TcpServer.class);

    protected final AtomicReference<ServerSocket> serverSocket = new AtomicReference<>();

    protected TcpServerConf serverConf = new TcpServerConf();
    protected TcpClientConf clientConf = new TcpClientConf();

    private Semaphore semaphore;
    protected final Set<TcpClient> clients = Collections.newSetFromMap(new ConcurrentHashMap<TcpClient, Boolean>());

    public TcpServer() {
    }

    /**
     * Inheriting classes must be able to provide a new client
     * 
     * @param socket
     * @return
     */
    protected abstract TcpClient newClient(Socket socket);

    /**
     * Clients notify them self when they are done
     * 
     * @param client
     */
    @Override
    public void clientStopped(TcpClient client) {
        clients.remove(client);
        semaphore.release();
    }

    @Override
    public void run() {
        // Initialize semaphore
        semaphore = new Semaphore(serverConf.getMaxClients());

        // Setup server socket
        try {
            serverSocket.set(new ServerSocket(serverConf.getPort()));
        } catch (IOException e) {
            LOG.error("Failed to setup server socket: " + e.getMessage());
            return;
        }
        // Accept incoming connections
        while (true) {
            Socket socket = null;
            try {
                // Maybe wait if max connections is exceeded
                try {
                    semaphore.acquire();
                } catch (InterruptedException e) {                    
                    break;
                }

                LOG.info("Waiting for connections on port " + serverConf.getPort());
                socket = serverSocket.get().accept();
                socket.setKeepAlive(true);
                LOG.info("Accepting connection from " + socket.getRemoteSocketAddress());
            } catch (IOException e) {
                if (!isInterrupted()) {
                    LOG.info(getName() + ": " + e.getMessage());
                }
                if (socket != null) {
                    try {
                        socket.close();
                    } catch (IOException ignored) {
                    }
                }
                semaphore.release();
                continue;
            }

            // Register and start client
            TcpClient client = newClient(socket);
            clients.add(client);
            client.start();

        }
                        
        // Stop clients
        for (TcpClient client : clients) {
            client.cancel();            
        }
        
        LOG.info("Stopped");

    }
    
    public void cancel() {
        this.interrupt();
        if (serverSocket.get() != null) {
            try {
                serverSocket.get().close();
            } catch (IOException ignored) {                
            }
        }
        try {
            this.join(AisBusComponent.THREAD_STOP_WAIT_MAX);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public TcpClientConf getClientConf() {
        return clientConf;
    }

    public void setClientConf(TcpClientConf clientConf) {
        this.clientConf = clientConf;
    }

    public TcpServerConf getServerConf() {
        return serverConf;
    }

    public void setServerConf(TcpServerConf serverConf) {
        this.serverConf = serverConf;
    }
    
    public Set<TcpClient> getClients() {
        return clients;
    }

}