之前一直采用.Net编写服务端程序，最近需要切换到Linux平台下，于是尝试采用Java编写数据服务器。TCP异步连接在C#中很容易实现，网上也有很多可供参考的代码。但Java异步TCP的参考资料较少，网上例程多是阻塞多线程方法，由于线程的开销较大，当客户端较多时系统资源的消耗也较大。
综合网上和书本的相关知识，本文给出一个Java TCP异步接收数据的代码示例，并给出相关的注释。
/**
* TcpAsyncServer.java
*/ import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.net.*;
import java.util.Iterator; public class TcpAsyncServer { /*监听端口*/
int port = 6000;
/*缓冲区大小*/
ByteBuffer buffer = ByteBuffer.allocate(1024);
/*其它相关定义*/
Selector selector;
ServerSocketChannel channel;
ServerSocket socket; /*启动*/
public void Start() throws Exception {
/*初始化一个Selector*/
selector = Selector.open();
/*打开通道*/
channel = ServerSocketChannel.open();
/*非阻塞模式*/
channel.configureBlocking(false);
/*本机IP*/
//InetAddress ip = InetAddress.getByName("127.0.0.1");
InetAddress ip = InetAddress.getLocalHost();
System.out.println(ip.toString());
/*绑定IP和端口*/
InetSocketAddress address = new InetSocketAddress(ip,port);
socket = channel.socket();
socket.bind(address);
/*启动监听*/
System.out.println("TCP服务器开始监听...");
Listen();
} /*停止*/
public void Stop() throws Exception {
channel.close();
selector.close();
} /*监听*/
public void Listen() throws Exception {
/*注册接收事件*/
channel.register(selector,SelectionKey.OP_ACCEPT);
/*无限循环*/
while (true) {
selector.select();
/*轮询事件*/
Iterator iter = selector.selectedKeys().iterator();
while (iter.hasNext()) {
SelectionKey key = (SelectionKey)iter.next();
iter.remove();
/*事件分类处理*/
if (key.isAcceptable()) {
ServerSocketChannel ssc = (ServerSocketChannel)key.channel();
SocketChannel sc = ssc.accept();
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ);
System.out.println("新终端已连接:"+ sc.getRemoteAddress());
}
else if (key.isReadable()) {
SocketChannel sc = (SocketChannel)key.channel();
int recvCount = sc.read(buffer);
if (recvCount > 0) {
byte[] arr = buffer.array();
System.out.println(sc.getRemoteAddress() + "发来数据: "+ new String(arr));
buffer.flip();
}
else {
sc.close();
}
buffer.clear();
} else { } } } } }
/**
* server.java
*/ public class server { public static void main(String[] args) throws Exception { TcpAsyncServer tcpServer = new TcpAsyncServer();
tcpServer.Start(); }
}
效果演示：
1. 利用TCP工具发送数据
3. 接收数据
