JAVA NIO Selector构建简单服务器

ゝ一纸荒年。 2022-04-22 06:44 263阅读 0赞

### JAVA NIO Selector构建简单服务器 ###

*  ServerSocketChannel + Selector
 *  SocketChannel
 *  UnitTest
 *  结果

# ServerSocketChannel + Selector #

NIOServer.java

public class NIOServer implements Runnable{ 
    
        private int clientNum = 0;
        private int bufferSize = 12;
    
        @Override
        public void run() { 
    
            try { 
                // 创建通道和选择器
                ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
                Selector selector = Selector.open();
                InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1", 5500);
                serverSocketChannel.socket().bind(inetSocketAddress);
                // 设置通道非阻塞 绑定选择器
                serverSocketChannel.configureBlocking(false);
                /* * ServerSocketChannel只有accept */
                serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT).attach("server");
                System.out.println("Server started .... port:5500");
    
                while(true) { 
                    int readyChannels = selector.select();
                    if(readyChannels == 0) continue;
                    Set selectedKeys = selector.selectedKeys();
                    Iterator keyIterator = selectedKeys.iterator();
                    while(keyIterator.hasNext()) { 
    
                        SelectionKey key = (SelectionKey)keyIterator.next();
                        // 判断是哪个事件
                        if(key.isAcceptable()) { // 客户请求连接
                            System.out.println(key.attachment()+ " - 接受请求事件");
                            ++clientNum;
                            // 获取通道 接受连接,
                            // 设置非阻塞模式（必须），同时需要注册 读写数据的事件，这样有消息触发时才能捕获
                            SocketChannel socketChannel = ((ServerSocketChannel) key.channel()).accept();
    
                            socketChannel.configureBlocking(false);
                            socketChannel.register(selector, SelectionKey.OP_READ).attach("accept"+clientNum);
    
                            System.out.println(key.attachment() + " - 已连接");
                        } else if (key.isConnectable()) { 
                            System.out.println(key.attachment()+ " - 连接事件");
                        } else if (key.isReadable()) { 
                            System.out.println(key.attachment()+ " - 读数据事件");
                            SocketChannel clientChannel=(SocketChannel)key.channel();
                            ByteBuffer receiveBuf = ByteBuffer.allocate(bufferSize);
                            clientChannel.read(receiveBuf);
                            System.out.println(key.attachment()+ " - 读取数据：" + getString(receiveBuf));
                        } else if (key.isWritable()) { 
                            System.out.println(key.attachment()+ " - 写数据事件");
                            SocketChannel clientChannel = (SocketChannel) key.channel();
                            ByteBuffer sendBuf = ByteBuffer.allocate(bufferSize);
                            String sendText = "helloc";
                            sendBuf.put(sendText.getBytes());
                            sendBuf.flip();        //写完数据后调用此方法
                            clientChannel.write(sendBuf);
                        }
                        keyIterator.remove();
                    }
                }
    
            } catch (Exception e) { 
                e.printStackTrace();
            }
    
        }
    
        public String getString(ByteBuffer buffer){ 
            StringBuffer builder = new StringBuffer("");
            try{ 
                for(int i = 0; i<buffer.position();i++){ 
                    builder.append((char)buffer.get(i));
                }
                return builder.toString();
            }catch (Exception ex){ 
                ex.printStackTrace();
                return builder.toString();
            }
        }
    }

# SocketChannel #

NIOClient.java

public class NIOClient implements Runnable { 
    
        private String tag = "client";
        private ByteBuffer readBuffer;
        private ByteBuffer writeBuffer;
        private boolean isConnected = false;
        private int bufferSize = 12;
    
        public NIOClient(String tag){ 
            this.tag = tag;
            readBuffer = ByteBuffer.allocate(bufferSize);
            writeBuffer = ByteBuffer.allocate(bufferSize);
        }
    
        @Override
        public void run() { 
    
            try { 
    
                Selector selector = Selector.open();
    
                SocketChannel socketChannel  = SocketChannel.open();
    
                socketChannel.configureBlocking(false);
                socketChannel.connect(new InetSocketAddress("127.0.0.1", 5500));
                socketChannel.register(selector, SelectionKey.OP_CONNECT | SelectionKey.OP_READ|SelectionKey.OP_WRITE).attach(tag);
    
                System.out.println(tag+" connect .... port:5500");
    
                while(true) { 
                    int readyChannels = selector.select();
                    if(readyChannels == 0) continue;
                    Set selectedKeys = selector.selectedKeys();
                    Iterator keyIterator = selectedKeys.iterator();
                    while(keyIterator.hasNext()) { 
    
                        SelectionKey key = (SelectionKey)keyIterator.next();
                        // 判断是哪个事件
                        if(key.isAcceptable()) { // 客户请求连接
                            System.out.println(key.attachment()+ "is accepted by server");
    
                        } else if (key.isConnectable()) { 
                            System.out.println(key.attachment()+ " connect ");
                            SocketChannel channel = (SocketChannel) key.channel();
                            if (channel.isConnectionPending()) { 
                                try { 
                                    /* * 人为将程序中止，等待连接创建完成,否则会报如下错误 * java.nio.channels.NotYetConnectedException at sun.nio.ch.SocketChannelImpl.ensureWriteOpen(SocketChannelImpl.java:274) */
                                    if (channel.finishConnect()) { 
                                        System.out.println(key.attachment()+" connect server succ");
                                        isConnected = true;
                                    }
                                } catch (IOException e) { 
                                    e.printStackTrace();
                                }
                            }
                        } else if (key.isReadable()) { 
                            System.out.println(key.attachment()+ " read ");
    
                            SocketChannel clientChannel = (SocketChannel) key.channel();
    
                            try { 
                                int len = clientChannel.read(readBuffer);
                                if (len == -1) { 
                                    System.out.println(key.attachment()+" read : len=-1");
                                    // 说明连接已经断开
                                    selector.close();
                                    socketChannel.close();
                                } else { 
                                    readBuffer.flip();
                                    byte[] buffer = new byte[len];
                                    readBuffer.get(buffer);
                                    readBuffer.clear();
                                    System.out.println(key.attachment()+" read : len=" + len + ", str=" + new String(buffer));
                                }
                            } catch (IOException e) { 
                                e.printStackTrace();
                            }
    
                        } else if (key.isWritable()) { 
                            System.out.println(key.attachment()+ " write ");
                            SocketChannel clientChannel = (SocketChannel) key.channel();
                            String str = "hellos";
                            byte[] buffer = str.getBytes();
                            writeBuffer.put(buffer);
                            writeBuffer.flip();
                            try { 
                                System.out.println(key.attachment()+ " write : len=" + buffer.length + ", str=" + str);
                                clientChannel.write(writeBuffer);
    
                                try { 
                                    Thread.sleep(100);
                                }catch (Exception e){ 
                                    e.printStackTrace();
                                }
                            } catch (IOException e) { 
                                e.printStackTrace();
                            }
                            writeBuffer.clear();
                        }
                        keyIterator.remove();
                    }
                }
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }
    
    }

# UnitTest #

@Test
        public void server(){ 
            Thread server = new Thread(new NIOServer());
            server.start();
    
            try { 
                Thread.sleep(200);
            } catch (InterruptedException e) { 
                e.printStackTrace();
            }
    
            Thread client1 = new Thread(new NIOClient("client1"));
            client1.start();
    
            Thread client2 = new Thread(new NIOClient("client2"));
            client2.start();
    
            try { 
                Thread.sleep(300);
            } catch (InterruptedException e) { 
                e.printStackTrace();
            }
    
    
            client1.stop();
            client2.stop();
    
            server.stop();
    	}

# 结果 #

![运行结果][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzQzMDAzNg_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzQzMDAzNg_size_16_color_FFFFFF_t_70]: /images/20220422/2d5e1e504a7e4f16a44154679d3b4dec.png