初识socket

百度词条

TCP 服务端：


```java
public class SocketService {

    public static void main(String[] args) throws IOException {
        //1 创建socket，指定监听端口
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("------创建socket，指定监听端口----");
        //2 当客户端没有链接9999端口时，程序阻塞，等待连接
        Socket accept = serverSocket.accept();
        System.out.println("------有客户端请求----");
        InputStream inputStream = accept.getInputStream();
        byte[] buf = new byte[1024];
        int readLen = 0;
        while ((readLen=inputStream.read(buf))!=-1){
            System.out.println(new String(buf,0,readLen));
        }
        inputStream.close();
        accept.close();
    }
}

TCP客户端

 public static void main(String[] args) throws Exception {
        // 1 链接指定服务及端口
        Socket socket = new Socket(InetAddress.getLocalHost(), 9999);
        System.out.println("-------链接成功------");
        // 发送数据
        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("-----：你好socket，我是第一个客户端".getBytes());
        // 关闭资源
        outputStream.close();
        socket.close();
    }

好了，简单的客户端服务端交互已经完成，先启动服务端，在启动客户端

UDP 接收端

public class UDPSocket2 {

    public static void main(String[] args) throws IOException {
        // UDP协议没有明确服务端和客户端之分，区别发送端和接收端,
        // 创建DatagramSocket对象，并指定监听端口
        DatagramSocket socket = new DatagramSocket(9999);
        byte[] bytes = new byte[1024];
        // 构建一个DatagramPacket 对象，准备接收数据
        DatagramPacket packet = new DatagramPacket(bytes, bytes.length);
        // 填充数据，调用接收数据对象，当监听到有数据发送到监听端口，就会接收
        // 否则会阻塞，等待接收数据
        socket.receive(packet);
        // 拆包，取出数据
        // 获取到实际数据长度
        int length = packet.getLength();
        byte[] data = packet.getData();
        String s = new String(data, 0, length);
        System.out.println("----UDPSocket2---接收到数据："+s);

        // 收到消息之后返回信息
        String str = "你好 UDP 1";
        DatagramPacket packetSend = new DatagramPacket(str.getBytes(), str.getBytes().length, InetAddress.getLocalHost(),9998);
        socket.send(packetSend);
        socket.close();
    }

UDP发送端

public class UDPSocket1 {

    public static void main(String[] args) throws IOException {
        // UDP协议没有明确服务端和客户端之分，区别发送端和接收端
        // 在9998端口中接收数据
        DatagramSocket socket = new DatagramSocket(9998);
        String str = "你好 UDP 2";
        byte[] bytes = str.getBytes();
        // 封装发送数据对象，发送内容，长度，目的服务及端口
        DatagramPacket packet = new DatagramPacket(bytes,bytes.length, InetAddress.getLocalHost(),9999);
        socket.send(packet);

        byte[] bytesReceive = new byte[1024];
        // 构建一个DatagramPacket 对象，准备接收数据
        DatagramPacket packetReceive = new DatagramPacket(bytes, bytes.length);
        // 填充数据，调用接收数据对象，当监听到有数据发送到监听端口，就会接收
        // 否则会阻塞，等待接收数据
        socket.receive(packetReceive);
        // 拆包，取出数据
        // 获取到实际数据长度
        int length = packet.getLength();
        byte[] data = packet.getData();
        String s = new String(data, 0, length);
        System.out.println("----UDPSocket1---接收到数据："+s);

        socket.close();
    }

}