做了一个指纹门锁，需要用TCP长连接进行服务端和门锁间的数据通信。
目前JAVA写socket服务端，门锁连接JAVA服务端。
服务端开了一个线程在监听门锁发来的数据（此处必须实时监听数据）
在监听的同时，若用socket发送数据的话，会出现异常报错。

第一个类负责接收socket连接

import java.io.IOException; import java.net.ServerSocket; import java.net.Socket;  import com.lock.util.StaticResource; /**  * 侦听类  * 不断侦听Socket连接，将连接的Socket记录，并开启线程接受传来的数据  * @author plzwb  */ public class ListenSocket implements Runnable{     ServerSocket serverSocket = null;          @Override     public void run() {         try {             serverSocket = new ServerSocket(2333);         } catch (IOException e) {             e.printStackTrace();             System.out.println("2333端口被占用");         }                  while (true) {             try {                 Socket socket = serverSocket.accept();                 StaticResource.socketList.add(socket);                 new Thread(new OpenRecordSocket(socket)).start();                 System.out.println("Socket已连接");             } catch (IOException e) {                 e.printStackTrace();                 System.out.println("accept异常");             }         }     } }

第二个类负责不断侦听数据

import java.io.IOException; import java.net.Socket;  import com.lock.util.SocketUtil; import com.lock.util.StaticResource;  public class OpenRecordSocket implements Runnable{     Socket socket = null;     SocketUtil socketUtil = null;     boolean state = true;           public OpenRecordSocket(Socket socket) {         this.socket = socket;         socketUtil = new SocketUtil(socket);     }          @Override     public void run() {         while(state){             try {                 System.out.println("准备接受");                 String text =  socketUtil.receiveData();                 System.out.println(text);             } catch (IOException e) {                 StaticResource.socketList.remove(socket);                 state = false;                 System.out.println("Socket已经删除");             }         }     } }

一个Servlet，访问即可调用socket发送消息

    public void doPost(HttpServletRequest request, HttpServletResponse response)             throws ServletException, IOException {         Socket socket = StaticResource.socketList.get(0);         SocketUtil socketUtil = new SocketUtil(socket);         socketUtil.sendData("hello");     }

Socket发送接收工具

import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.Socket;  public class SocketUtil {     Socket socket = null;      public SocketUtil(Socket socket) {         super();         this.socket = socket;     }          //发送数据     public void sendData(String data) throws IOException {         OutputStream outputStream = socket.getOutputStream();         outputStream.write(data.getBytes());     }          //接收数据     public String receiveData() throws IOException {         InputStream inputStream = socket.getInputStream();         byte[] buf = new byte[1024];         int len = inputStream.read(buf);         String text = new String(buf, 0, len);         return text;     } }

异常信息如下

Exception in thread "Thread-3"  java.lang.StringIndexOutOfBoundsException: String index out of range: -1     at java.lang.String.checkBounds(String.java:381)     at java.lang.String.<init>(String.java:545)     at com.lock.util.SocketUtil.receiveData(SocketUtil.java:27)      at com.lock.socket.OpenRecordSocket.run(OpenRecordSocket.java:25)     at java.lang.Thread.run(Thread.java:745)