Java - Socket shutdownOutput() 方法

描述

Java Socket shutdownOutput() 用于禁用此套接字的输出流。对于 TCP 套接字，任何先前写入的数据将在 TCP 的正常连接终止序列后发送。如果在套接字上调用 shutdownOutput() 后写入套接字输出流，则该流将抛出 IOException。

声明

以下是 java.net.Socket.shutdownOutput() 方法的声明。

public void shutdownOutput() throws IOException

参数

无

返回值

无

异常

IOException − 如果在关闭此套接字时发生 I/O 错误。

示例

以下示例演示了如何使用 Java Socket shutdownOutput() 方法来禁用此套接字的输出流。第一步，我们创建了一个 GreetingClient 类，其中我们使用命令行参数读取服务器名称和端口。使用提供的服务器名称和端口，创建一个作为客户端的 Socket 实例。使用 client.getInputStream()，我们读取服务器发送的内容。然后将 InputStream 实例转换为 DataInputStream，并使用 DataInputStream.readUTF() 方法打印。由于我们在 writeUTF() 方法调用之前调用了 shutdownOutput()，因此此代码引发异常，如程序输出所示。

以下 GreetingClient 程序是客户端应用程序的示例，该应用程序使用 Socket 类在命令行参数指定的端口号上侦听服务器输出 -

package com.tutorialspoint;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;

public class GreetingClient {

   public static void main(String [] args) {
      String serverName = args[0];
      int port = Integer.parseInt(args[1]);
      try {
         System.out.println("Connecting to " + serverName + " on port " + port);
         Socket client = new Socket(serverName, port);
         
         System.out.println("Just connected to " + client.getRemoteSocketAddress());
         OutputStream outToServer = client.getOutputStream();
         DataOutputStream out = new DataOutputStream(outToServer);
         
         out.writeUTF("Hello from " + client.getLocalSocketAddress());
         InputStream inFromServer = client.getInputStream();
         DataInputStream in = new DataInputStream(inFromServer);
         
         System.out.println("Server says " + in.readUTF());
         client.close();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

以下 GreetingServer 程序是服务器应用程序的示例，该应用程序使用 Socket 类在命令行参数指定的端口号上侦听客户端 -

package com.tutorialspoint;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketTimeoutException;

public class GreetingServer extends Thread {
   private ServerSocket serverSocket;
   
   public GreetingServer(int port) throws IOException {
      serverSocket = new ServerSocket(port);
      serverSocket.setSoTimeout(10000);
   }

   public void run() {
      while(true) {
         try {
            System.out.println("Waiting for client on port " + 
               serverSocket.getLocalPort() + "...");
            Socket server = serverSocket.accept();
            
            System.out.println("Just connected to " + server.getRemoteSocketAddress());
            DataInputStream in = new DataInputStream(server.getInputStream());
            
            System.out.println(in.readUTF());
            DataOutputStream out = new DataOutputStream(server.getOutputStream());
            server.shutdownOutput();
            out.writeUTF("Thank you for connecting to " + server.getLocalSocketAddress()
               + "\nGoodbye!");
            server.close();
            
         } catch (SocketTimeoutException s) {
            System.out.println("Socket timed out!");
            break;
         } catch (IOException e) {
            e.printStackTrace();
            break;
         }
      }
   }
   
   public static void main(String [] args) {
      int port = Integer.parseInt(args[0]);
      try {
         Thread t = new GreetingServer(port);
         t.start();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

编译客户端和服务器，然后按如下方式启动服务器 -

Waiting for client on port 6066...
Just connected to /127.0.0.1:60982
Hello from /127.0.0.1:60982
java.net.SocketException: Cannot send after socket shutdown: socket write error
	at java.base/java.net.SocketOutputStream.socketWrite0(Native Method)
	at java.base/java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:110)
	at java.base/java.net.SocketOutputStream.write(SocketOutputStream.java:150)
	at java.base/java.io.DataOutputStream.write(DataOutputStream.java:107)
	at java.base/java.io.DataOutputStream.writeUTF(DataOutputStream.java:401)
	at java.base/java.io.DataOutputStream.writeUTF(DataOutputStream.java:323)
	at com.tutorialspoint.GreetingServer.run(GreetingServer.java:31)

按如下方式检查客户端程序 -

输出

Connecting to localhost on port 6066
Just connected to localhost/127.0.0.1:6066
java.io.EOFException
	at java.base/java.io.DataInputStream.readUnsignedShort(DataInputStream.java:345)
	at java.base/java.io.DataInputStream.readUTF(DataInputStream.java:594)
	at java.base/java.io.DataInputStream.readUTF(DataInputStream.java:569)
	at com.tutorialspoint.GreetingClient.main(GreetingClient.java:28)
	at com.tutorialspoint.GreetingClient.main(GreetingClient.java:28)