java的Socket通信例子及关于java.net.SocketException: Socket is closed错误

今天写socket数据相互通信的时候,碰到一个及其蛋疼的错误。单向传输数据的时候server与client是没有问题的,但是两个都有输入输出操作的时候就出现了这个问题 java.net.SocketException: Socket is closed:

下面附代码:

Server:

        StringBuffer result = new StringBuffer("");
        int port = 9090;
        //定义一个ServerSocket监听在端口9090上
        ServerSocket server = null;

        while(true){//注意while放在哪

            try {

                server = new ServerSocket(port);
                //server尝试接收其他Socket的连接请求，server的accept方法是阻塞式的
                Socket client = server.accept();
                server.setSoTimeout(20*1000);
                System.out.println("client connected!");

                //接收消息
                Reader read = new InputStreamReader(client.getInputStream());
                BufferedReader bufferReader = new BufferedReader(read);
                String readLine = "";
                //bufferReader.readLine()用一次读一行,前面用过再用就是下一行
                while((readLine = bufferReader.readLine()) != null){
                    result.append(readLine);
                }
                bufferReader.close;
                System.out.println("from client: " + result.toString());  

                //boolean isConnected = socket.isConnected() && !socket.isClosed();

                //读完后写一句
                OutputStream os = client.getOutputStream();//这一行会报socket关闭的错误
                DataOutputStream out = new DataOutputStream(os);
                out.writeBytes("Hello Client,I'm Server!");
                System.out.println("sent mesg");

                out.flush();//清空缓存
                out.close();//关闭
                client.close();  

            } catch (IOException e) {
                e.printStackTrace();
            } finally {//这里socket.close最好放在finally里
                try
                {
                    if(server != null){
                        server.close();
                    }
                }catch(IOException e){
                    e.printStackTrace();
                }
            }   

　　　　}         

Client: 
        StringBuffer result = new StringBuffer("") ;
        String host = "192.168.0.88";
        int port = 9090;
        Socket client = null;

        try
        {
             System.out.println("Connecting to " + host + " on port " + port);
             client = new Socket(host, port);
             client.setSoTimeout(20*1000);
             System.out.println("Just connected to " + client.getRemoteSocketAddress());
             　　　　　　　 //发送消息
             OutputStream os = client.getOutputStream();
             DataOutputStream out = new DataOutputStream(os);
             out.writeBytes("Hello Server!");
             System.out.println("sent mesg");
             out.flush();//清空缓存
             out.close();//关闭
//接收消息
             Reader read = new InputStreamReader(client.getInputStream());//同样这里会报错
             BufferedReader bufferReader = new BufferedReader(read);
             String readLine = "";
             while((readLine = bufferReader.readLine()) != null){
                 result.append(readLine);
             }
             System.out.println("from Server: " + result.toString());
             bufferReader.close;

          }catch(IOException e){
             e.printStackTrace();
          } finally {
                try
                {
                    if(client != null){
                        client.close();
                    }
                }catch(IOException e){
                    e.printStackTrace();
                }
          }

找了很久终于找到 bufferReader.close()与out.close()关闭会直接导致sockect.close()故只进行输入输出中的一个之后就出现java.net.SocketException: Socket is closed:错误,可能是因为用到了socket.getOutputStream(),socket.getInputStream()的缘故。

这里将out.close()与bufferReader.close()兑换成client.shutdownOutput()与client.shutdownInput();之后就不会出现Socket直接被关闭的问题了。

Socket.close()->输入输出流都被关闭->有时候希望仅关闭输入流或输出流之一->Socket半关闭方法->shutdownInput():仅关闭输入流shutdownOutput():仅关闭输出流

上述问题中如果把bufferReader.close()与out.close()放在最后,就会出现Server在read的时候因为Client未关闭outputstream一直傻等下去。故此种方法不可取。