/*
 * This file is part of lanterna (http://code.google.com/p/lanterna/).
 *
 * lanterna is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Copyright (C) 2010-2020 Martin Berglund
 */
package com.googlecode.lanterna.terminal.ansi;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.Charset;
import javax.net.ServerSocketFactory;

This class implements a Telnet server, capable of accepting multiple clients and presenting each one as their own Terminal. You need to tell it at least what port to listen on and then it create a Server socket listening for incoming connections. Use acceptConnection() to wait for the next incoming connection, it will be returned as a TelnetTerminal object that represents the client and which will be the way for the server to send content to this client. Next connecting client (through acceptConnection() will get a different TelnetTerminal, i.e. their content will not be in sync automatically but considered as two different terminals. 
Author:
martin
See Also:
TelnetTerminal
Wikipedia/**
 * This class implements a Telnet server, capable of accepting multiple clients and presenting each one as their own
 * Terminal. You need to tell it at least what port to listen on and then it create a Server socket listening for
 * incoming connections. Use {@code acceptConnection()} to wait for the next incoming connection, it will be returned as
 * a {@code TelnetTerminal} object that represents the client and which will be the way for the server to send content
 * to this client. Next connecting client (through {@code acceptConnection()} will get a different
 * {@code TelnetTerminal}, i.e. their content will not be in sync automatically but considered as two different
 * terminals.
 * @author martin
 * @see TelnetTerminal
 * @see <a href="http://en.wikipedia.org/wiki/Telnet">Wikipedia</a>
 */
@SuppressWarnings("WeakerAccess")
public class TelnetTerminalServer {
    private final Charset charset;
    private final ServerSocket serverSocket;

    
Creates a new TelnetTerminalServer on a specific port
Params:
port – Port to listen for incoming telnet connections
Throws:
IOException – If there was an underlying I/O exception/**
     * Creates a new TelnetTerminalServer on a specific port
     * @param port Port to listen for incoming telnet connections
     * @throws IOException If there was an underlying I/O exception
     */
    public TelnetTerminalServer(int port) throws IOException {
        this(ServerSocketFactory.getDefault(), port);
    }

    
Creates a new TelnetTerminalServer on a specific port, using a certain character set
Params:
port – Port to listen for incoming telnet connections
charset – Character set to use
Throws:
IOException – If there was an underlying I/O exception/**
     * Creates a new TelnetTerminalServer on a specific port, using a certain character set
     * @param port Port to listen for incoming telnet connections
     * @param charset Character set to use
     * @throws IOException If there was an underlying I/O exception
     */
    public TelnetTerminalServer(int port, Charset charset) throws IOException {
        this(ServerSocketFactory.getDefault(), port, charset);
    }

    
Creates a new TelnetTerminalServer on a specific port through a ServerSocketFactory
Params:
port – Port to listen for incoming telnet connections
serverSocketFactory – ServerSocketFactory to use when creating the ServerSocket
Throws:
IOException – If there was an underlying I/O exception/**
     * Creates a new TelnetTerminalServer on a specific port through a ServerSocketFactory
     * @param port Port to listen for incoming telnet connections
     * @param serverSocketFactory ServerSocketFactory to use when creating the ServerSocket
     * @throws IOException If there was an underlying I/O exception
     */
    public TelnetTerminalServer(ServerSocketFactory serverSocketFactory, int port) throws IOException {
        this(serverSocketFactory, port, Charset.defaultCharset());
    }

    
Creates a new TelnetTerminalServer on a specific port through a ServerSocketFactory with a certain Charset
Params:
serverSocketFactory – ServerSocketFactory to use when creating the ServerSocket
port – Port to listen for incoming telnet connections
charset – Character set to use
Throws:
IOException – If there was an underlying I/O exception/**
     * Creates a new TelnetTerminalServer on a specific port through a ServerSocketFactory with a certain Charset
     * @param serverSocketFactory ServerSocketFactory to use when creating the ServerSocket
     * @param port Port to listen for incoming telnet connections
     * @param charset Character set to use
     * @throws IOException If there was an underlying I/O exception
     */
    public TelnetTerminalServer(ServerSocketFactory serverSocketFactory, int port, Charset charset) throws IOException {
        this.serverSocket = serverSocketFactory.createServerSocket(port);
        this.charset = charset;
    }

    
Returns the actual server socket used by this object. Can be used to tweak settings but be careful!
Returns:
Underlying ServerSocket/**
     * Returns the actual server socket used by this object. Can be used to tweak settings but be careful!
     * @return Underlying ServerSocket
     */
    public ServerSocket getServerSocket() {
        return serverSocket;
    }

    
Waits for the next client to connect in to our server and returns a Terminal implementation, TelnetTerminal, that
represents the remote terminal this client is running. The terminal can be used just like any other Terminal, but
keep in mind that all operations are sent over the network.
Throws:
IOException – If there was an underlying I/O exception
Returns:
TelnetTerminal for the remote client's terminal/**
     * Waits for the next client to connect in to our server and returns a Terminal implementation, TelnetTerminal, that
     * represents the remote terminal this client is running. The terminal can be used just like any other Terminal, but
     * keep in mind that all operations are sent over the network.
     * @return TelnetTerminal for the remote client's terminal
     * @throws IOException If there was an underlying I/O exception
     */
    public TelnetTerminal acceptConnection() throws IOException {
        Socket clientSocket = serverSocket.accept();
        clientSocket.setTcpNoDelay(true);
        return new TelnetTerminal(clientSocket, charset);
    }

    
Closes the server socket, accepting no new connection. Any call to acceptConnection() after this will fail.
Throws:
IOException – If there was an underlying I/O exception/**
     * Closes the server socket, accepting no new connection. Any call to acceptConnection() after this will fail.
     * @throws IOException If there was an underlying I/O exception
     */
    public void close() throws IOException {
        serverSocket.close();
    }
}