Add logic to retry opening serial port connections if they are broken

.classpath

@@ -10,6 +10,7 @@
 		<attributes>
 			<attribute name="optional" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">

.settings/org.eclipse.jdt.core.prefs

@@ -2,4 +2,5 @@ eclipse.preferences.version=1
 org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.8
 org.eclipse.jdt.core.compiler.compliance=1.8
 org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
+org.eclipse.jdt.core.compiler.release=disabled
 org.eclipse.jdt.core.compiler.source=1.8

RELEASE-NOTES

@@ -1,5 +1,6 @@
 *Release notes for 3.0.6*
 * Add ability to validate slave ID in responses.  Defaults to enabled for Ascii, RTU and Encapsulated TCP, disabled for Tcp and Udp
+* Add retry to serial connections if the connection is broken try to re-open the serial port retries number of times
 
 *Release notes for 3.0.4*
 * TcpMaster now allows optionally controlling transaction id.

src/com/serotonin/modbus4j/ip/tcp/TcpMaster.java

@@ -5,12 +5,12 @@
  *
  * Copyright (C) 2006-2011 Serotonin Software Technologies Inc. http://serotoninsoftware.com
  * @author Matthew Lohbihler
- * 
+ *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
- * 
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ -60,7 +60,7 @@ public class TcpMaster extends ModbusMaster {
     private static final int RETRY_PAUSE_MAX = 1000;
 
     // Configuration fields.
-	private final Log LOG = LogFactory.getLog(TcpMaster.class);
+    private final Log LOG = LogFactory.getLog(TcpMaster.class);
     private short nextTransactionId = 0;
     private final IpParameters ipParameters;
     private final boolean keepAlive;
@@ -73,7 +73,7 @@ public class TcpMaster extends ModbusMaster {
 
     /**
      * <p>Constructor for TcpMaster.</p>
-     * 
+     *
      * @param params
      * @param keepAlive
      * @param autoIncrementTransactionId
@@ -84,11 +84,11 @@ public class TcpMaster extends ModbusMaster {
         this.keepAlive = keepAlive;
         this.autoIncrementTransactionId = autoIncrementTransactionId;
     }
-    
+
     /**
      * <p>Constructor for TcpMaster.</p>
      * Default to not validating the slave id in responses
-     * 
+     *
      * @param params a {@link com.serotonin.modbus4j.ip.IpParameters} object.
      * @param keepAlive a boolean.
      * @param autoIncrementTransactionId a boolean.
@@ -96,11 +96,11 @@ public class TcpMaster extends ModbusMaster {
     public TcpMaster(IpParameters params, boolean keepAlive, boolean autoIncrementTransactionId) {
         this(params, keepAlive, autoIncrementTransactionId, false);
     }
-    
-    
+
+
     /**
      * <p>Constructor for TcpMaster.</p>
-     * 
+     *
      * Default to auto increment transaction id
      * Default to not validating the slave id in responses
      *
@@ -119,7 +119,7 @@ public class TcpMaster extends ModbusMaster {
     public void setNextTransactionId(short id) {
         this.nextTransactionId = id;
     }
-    
+
     /**
      * <p>Getter for the field <code>nextTransactionId</code>.</p>
      *
@@ -158,9 +158,9 @@ public class TcpMaster extends ModbusMaster {
                 openConnection();
 
             if(conn == null){
-            	LOG.debug("Connection null: " +  ipParameters.getPort());
-        	}
-            
+                LOG.debug("Connection null: " +  ipParameters.getPort());
+            }
+
         }
         catch (Exception e) {
             closeConnection();
@@ -178,56 +178,56 @@ public class TcpMaster extends ModbusMaster {
         }
 
         if(LOG.isDebugEnabled()){
-	    	StringBuilder sb = new StringBuilder();
-	        for (byte b : Arrays.copyOfRange(ipRequest.getMessageData(),0,ipRequest.getMessageData().length)) {
-	            sb.append(String.format("%02X ", b));
-	        }
-			LOG.debug("Encap Request: " + sb.toString());
+            StringBuilder sb = new StringBuilder();
+            for (byte b : Arrays.copyOfRange(ipRequest.getMessageData(),0,ipRequest.getMessageData().length)) {
+                sb.append(String.format("%02X ", b));
+            }
+            LOG.debug("Encap Request: " + sb.toString());
         }
 
-		// Send the request to get the response.
+        // Send the request to get the response.
         IpMessageResponse ipResponse;
-    	LOG.debug("Sending on port: " +  ipParameters.getPort());
+        LOG.debug("Sending on port: " +  ipParameters.getPort());
         try {
-        	if(conn == null){
-            	LOG.debug("Connection null: " +  ipParameters.getPort());
-        	}
+            if(conn == null){
+                LOG.debug("Connection null: " +  ipParameters.getPort());
+            }
             ipResponse = (IpMessageResponse) conn.send(ipRequest);
             if (ipResponse == null)
                 return null;
-            
+
             if(LOG.isDebugEnabled()){
-    	    	StringBuilder sb = new StringBuilder();
-	            for (byte b : Arrays.copyOfRange(ipResponse.getMessageData(),0,ipResponse.getMessageData().length)) {
-	                sb.append(String.format("%02X ", b));
-	            }
-				LOG.debug("Response: " + sb.toString());
+                StringBuilder sb = new StringBuilder();
+                for (byte b : Arrays.copyOfRange(ipResponse.getMessageData(),0,ipResponse.getMessageData().length)) {
+                    sb.append(String.format("%02X ", b));
+                }
+                LOG.debug("Response: " + sb.toString());
             }
             return ipResponse.getModbusResponse();
         }
         catch (Exception e) {
-			LOG.debug("Exception: " + e.getMessage() + " " + e.getLocalizedMessage());
+            LOG.debug("Exception: " + e.getMessage() + " " + e.getLocalizedMessage());
             if (keepAlive) {
-    			LOG.debug("KeepAlive - reconnect!");
+                LOG.debug("KeepAlive - reconnect!");
                 // The connection may have been reset, so try to reopen it and attempt the message again.
                 try {
-                	LOG.debug("Modbus4J: Keep-alive connection may have been reset. Attempting to re-open.");
+                    LOG.debug("Modbus4J: Keep-alive connection may have been reset. Attempting to re-open.");
                     openConnection();
                     ipResponse = (IpMessageResponse) conn.send(ipRequest);
                     if (ipResponse == null)
                         return null;
                     if(LOG.isDebugEnabled()){
-            	    	StringBuilder sb = new StringBuilder();
-	                    for (byte b : Arrays.copyOfRange(ipResponse.getMessageData(),0,ipResponse.getMessageData().length)) {
-	                        sb.append(String.format("%02X ", b));
-	                    }
-	        			LOG.debug("Response: " + sb.toString());
+                        StringBuilder sb = new StringBuilder();
+                        for (byte b : Arrays.copyOfRange(ipResponse.getMessageData(),0,ipResponse.getMessageData().length)) {
+                            sb.append(String.format("%02X ", b));
+                        }
+                        LOG.debug("Response: " + sb.toString());
                     }
                     return ipResponse.getModbusResponse();
                 }
                 catch (Exception e2) {
                     closeConnection();
-        			LOG.debug("Exception: " + e2.getMessage() + " " + e2.getLocalizedMessage());
+                    LOG.debug("Exception: " + e2.getMessage() + " " + e2.getLocalizedMessage());
                     throw new ModbusTransportException(e2, request.getSlaveId());
                 }
             }
@@ -268,7 +268,7 @@ public class TcpMaster extends ModbusMaster {
 
                 if (retries <= 0)
                     throw e;
-                // System.out.println("Modbus4J: Open connection failed, trying again.");
+
                 retries--;
 
                 // Pause for a bit.

src/com/serotonin/modbus4j/serial/SerialMaster.java

@@ -5,12 +5,12 @@
  *
  * Copyright (C) 2006-2011 Serotonin Software Technologies Inc. http://serotoninsoftware.com
  * @author Matthew Lohbihler
- * 
+ *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
- * 
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ -26,6 +26,7 @@ import org.apache.commons.logging.LogFactory;
 import com.serotonin.modbus4j.ModbusMaster;
 import com.serotonin.modbus4j.exception.ModbusInitException;
 import com.serotonin.modbus4j.sero.messaging.EpollStreamTransport;
+import com.serotonin.modbus4j.sero.messaging.MessageControl;
 import com.serotonin.modbus4j.sero.messaging.StreamTransport;
 import com.serotonin.modbus4j.sero.messaging.Transport;
 
@@ -36,19 +37,22 @@ import com.serotonin.modbus4j.sero.messaging.Transport;
  * @version 5.0.0
  */
 abstract public class SerialMaster extends ModbusMaster {
-	
-	
-	private final Log LOG = LogFactory.getLog(SerialMaster.class);
 
-	// Runtime fields.
+    private static final int RETRY_PAUSE_START = 50;
+    private static final int RETRY_PAUSE_MAX = 1000;
+
+    private final Log LOG = LogFactory.getLog(SerialMaster.class);
+
+    // Runtime fields.
+    protected boolean serialPortOpen;
     protected SerialPortWrapper wrapper;
     protected Transport transport;
 
-    
-    
+
+
     /**
      * <p>Constructor for SerialMaster.</p>
-     * 
+     *
      * Default to validating the slave id in responses
      *
      * @param wrapper a {@link com.serotonin.modbus4j.serial.SerialPortWrapper} object.
@@ -56,7 +60,7 @@ abstract public class SerialMaster extends ModbusMaster {
     public SerialMaster(SerialPortWrapper wrapper) {
         this(wrapper, true);
     }
-    
+
     /**
      * <p>Constructor for SerialMaster.</p>
      * @param wrapper a {@link com.serotonin.modbus4j.serial.SerialPortWrapper} object.
@@ -71,28 +75,90 @@ abstract public class SerialMaster extends ModbusMaster {
     @Override
     public void init() throws ModbusInitException {
         try {
-            
-        	this.wrapper.open();
-            
-            if (getePoll() != null)
-                transport = new EpollStreamTransport(wrapper.getInputStream(), wrapper.getOutputStream(),
-                        getePoll());
-            else
-                transport = new StreamTransport(wrapper.getInputStream(), wrapper.getOutputStream());
+            this.openConnection(null);
         }
         catch (Exception e) {
             throw new ModbusInitException(e);
         }
     }
 
+    /**
+     * Open the serial port and initialize the transport, ensure
+     * connection is closed first
+     *
+     * @param conn
+     * @throws Exception
+     */
+    protected void openConnection(MessageControl toClose) throws Exception {
+        // Make sure any existing connection is closed.
+        closeConnection(toClose);
+
+        // Try 'retries' times to get the socket open.
+        int retries = getRetries();
+        int retryPause = RETRY_PAUSE_START;
+        while (true) {
+            try {
+                this.wrapper.open();
+                this.serialPortOpen = true;
+                if (getePoll() != null) {
+                    transport = new EpollStreamTransport(wrapper.getInputStream(),
+                            wrapper.getOutputStream(),
+                            getePoll());
+                }else {
+                    transport = new StreamTransport(wrapper.getInputStream(),
+                            wrapper.getOutputStream());
+                }
+                break;
+            }catch(Exception e) {
+                //Ensure port is closed before we try to reopen or bail out
+                close();
+
+                if (retries <= 0)
+                    throw e;
+
+                retries--;
+
+                // Pause for a bit.
+                try {
+                    Thread.sleep(retryPause);
+                }
+                catch (InterruptedException e1) {
+                    // ignore
+                }
+                retryPause *= 2;
+                if (retryPause > RETRY_PAUSE_MAX)
+                    retryPause = RETRY_PAUSE_MAX;
+            }
+        }
+    }
+
+    /**
+     * Close serial port
+     * @param conn
+     */
+    protected void closeConnection(MessageControl conn) {
+        closeMessageControl(conn);
+        try {
+            if(serialPortOpen) {
+                wrapper.close();
+                serialPortOpen = false;
+            }
+        }
+        catch (Exception e) {
+            getExceptionHandler().receivedException(e);
+        }
+
+        transport = null;
+    }
+
     /**
      * <p>close.</p>
      */
     public void close() {
         try {
-			wrapper.close();
-		} catch (Exception e) {
-			LOG.error(e.getMessage(), e);
-		}
+            wrapper.close();
+        } catch (Exception e) {
+            LOG.error(e.getMessage(), e);
+        }
     }
 }

src/com/serotonin/modbus4j/serial/ascii/AsciiMaster.java

@@ -5,12 +5,12 @@
  *
  * Copyright (C) 2006-2011 Serotonin Software Technologies Inc. http://serotoninsoftware.com
  * @author Matthew Lohbihler
- * 
+ *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
- * 
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ -20,7 +20,8 @@
  */
 package com.serotonin.modbus4j.serial.ascii;
 
-import java.io.IOException;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 
 import com.serotonin.modbus4j.exception.ModbusInitException;
 import com.serotonin.modbus4j.exception.ModbusTransportException;
@@ -39,21 +40,23 @@ import com.serotonin.modbus4j.sero.messaging.StreamTransport;
  * @version 5.0.0
  */
 public class AsciiMaster extends SerialMaster {
+    private final Log LOG = LogFactory.getLog(SerialMaster.class);
+
     private MessageControl conn;
 
     /**
      * <p>Constructor for AsciiMaster.</p>
-     * 
+     *
      * Default to validating the slave id in responses
-     * 
+     *
      * @param wrapper a {@link com.serotonin.modbus4j.serial.SerialPortWrapper} object.
      */
     public AsciiMaster(SerialPortWrapper wrapper) {
         super(wrapper, true);
     }
-    
+
     /**
-     * 
+     *
      * @param wrapper a {@link com.serotonin.modbus4j.serial.SerialPortWrapper} object.
      * @param validateResponse - confirm that requested slave id is the same in the response
      */
@@ -64,21 +67,26 @@ public class AsciiMaster extends SerialMaster {
     /** {@inheritDoc} */
     @Override
     public void init() throws ModbusInitException {
-        super.init();
-
-        AsciiMessageParser asciiMessageParser = new AsciiMessageParser(true);
-        conn = getMessageControl();
         try {
-            conn.start(transport, asciiMessageParser, null, new SerialWaitingRoomKeyFactory());
-            if (getePoll() == null)
-                ((StreamTransport) transport).start("Modbus ASCII master");
+            openConnection(null);
         }
-        catch (IOException e) {
+        catch (Exception e) {
             throw new ModbusInitException(e);
         }
         initialized = true;
     }
 
+    @Override
+    protected void openConnection(MessageControl toClose) throws Exception {
+        super.openConnection(toClose);
+        AsciiMessageParser asciiMessageParser = new AsciiMessageParser(true);
+        this.conn = getMessageControl();
+        this.conn.start(transport, asciiMessageParser, null, new SerialWaitingRoomKeyFactory());
+        if (getePoll() == null) {
+            ((StreamTransport) transport).start("Modbus ASCII master");
+        }
+    }
+
     /** {@inheritDoc} */
     @Override
     public void destroy() {
@@ -102,7 +110,18 @@ public class AsciiMaster extends SerialMaster {
             return asciiResponse.getModbusResponse();
         }
         catch (Exception e) {
-            throw new ModbusTransportException(e, request.getSlaveId());
+            try {
+                LOG.debug("Connection may have been reset. Attempting to re-open.");
+                openConnection(conn);
+                asciiResponse = (AsciiMessageResponse) conn.send(asciiRequest);
+                if (asciiResponse == null)
+                    return null;
+                return asciiResponse.getModbusResponse();
+            }catch(Exception e2) {
+                closeConnection(conn);
+                LOG.debug("Failed to re-connect", e);
+                throw new ModbusTransportException(e2, request.getSlaveId());
+            }
         }
     }
 }

src/com/serotonin/modbus4j/serial/rtu/RtuMaster.java

@@ -5,12 +5,12 @@
  *
  * Copyright (C) 2006-2011 Serotonin Software Technologies Inc. http://serotoninsoftware.com
  * @author Matthew Lohbihler
- * 
+ *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
- * 
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ -20,7 +20,8 @@
  */
 package com.serotonin.modbus4j.serial.rtu;
 
-import java.io.IOException;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 
 import com.serotonin.modbus4j.exception.ModbusInitException;
 import com.serotonin.modbus4j.exception.ModbusTransportException;
@@ -40,24 +41,26 @@ import com.serotonin.modbus4j.sero.messaging.StreamTransport;
  * @version 5.0.0
  */
 public class RtuMaster extends SerialMaster {
-	
+
+    private final Log LOG = LogFactory.getLog(RtuMaster.class);
+
     // Runtime fields.
     private MessageControl conn;
-    
+
     /**
      * <p>Constructor for RtuMaster.</p>
-     * 
+     *
      * Default to validating the slave id in responses
-     * 
+     *
      * @param wrapper a {@link com.serotonin.modbus4j.serial.SerialPortWrapper} object.
      */
     public RtuMaster(SerialPortWrapper wrapper) {
         super(wrapper, true);
     }
-    
+
     /**
      * <p>Constructor for RtuMaster.</p>
-     * 
+     *
      * @param wrapper a {@link com.serotonin.modbus4j.serial.SerialPortWrapper} object.
      * @param validateResponse - confirm that requested slave id is the same in the response
      */
@@ -68,21 +71,28 @@ public class RtuMaster extends SerialMaster {
     /** {@inheritDoc} */
     @Override
     public void init() throws ModbusInitException {
-        super.init();
-
-        RtuMessageParser rtuMessageParser = new RtuMessageParser(true);
-        conn = getMessageControl();
         try {
-            conn.start(transport, rtuMessageParser, null, new SerialWaitingRoomKeyFactory());
-            if (getePoll() == null)
-                ((StreamTransport) transport).start("Modbus RTU master");
+            openConnection(null);
         }
-        catch (IOException e) {
+        catch (Exception e) {
             throw new ModbusInitException(e);
         }
         initialized = true;
     }
 
+    /** {@inheritDoc} */
+    @Override
+    protected void openConnection(MessageControl toClose) throws Exception {
+        super.openConnection(toClose);
+
+        RtuMessageParser rtuMessageParser = new RtuMessageParser(true);
+        this.conn = getMessageControl();
+        this.conn.start(transport, rtuMessageParser, null, new SerialWaitingRoomKeyFactory());
+        if (getePoll() == null) {
+            ((StreamTransport) transport).start("Modbus RTU master");
+        }
+    }
+
     /** {@inheritDoc} */
     @Override
     public void destroy() {
@@ -106,13 +116,21 @@ public class RtuMaster extends SerialMaster {
             return rtuResponse.getModbusResponse();
         }
         catch (Exception e) {
-            throw new ModbusTransportException(e, request.getSlaveId());
-        }
-        finally {
-            
+            try {
+                LOG.debug("Connection may have been reset. Attempting to re-open.");
+                openConnection(conn);
+                rtuResponse = (RtuMessageResponse) conn.send(rtuRequest);
+                if (rtuResponse == null)
+                    return null;
+                return rtuResponse.getModbusResponse();
+            }catch(Exception e2) {
+                closeConnection(conn);
+                LOG.debug("Failed to re-connect", e);
+                throw new ModbusTransportException(e2, request.getSlaveId());
+            }
         }
     }
-    
+
     /**
      * RTU Spec:
      * For baud greater than 19200
@@ -130,7 +148,7 @@ public class RtuMaster extends SerialMaster {
             return 1750000l; //Nanoseconds
         }
         else {
-        	float charTime = computeCharacterTime(wrapper);
+            float charTime = computeCharacterTime(wrapper);
             return (long) (charTime * 3.5f);
         }
     }
@@ -152,12 +170,12 @@ public class RtuMaster extends SerialMaster {
             return 750000l; //Nanoseconds
         }
         else {
-        	float charTime = computeCharacterTime(wrapper);
+            float charTime = computeCharacterTime(wrapper);
             return (long) (charTime * 1.5f);
         }
     }
 
-    
+
     /**
      * Compute the time it takes to transmit 1 character with
      * the provided Serial Parameters.
@@ -178,18 +196,18 @@ public class RtuMaster extends SerialMaster {
         //Compute the char size
         float charBits = wrapper.getDataBits();
         switch (wrapper.getStopBits()) {
-        case 1:
-            //Strangely this results in 0 stop bits.. in JSSC code
-            break;
-        case 2:
-            charBits += 2f;
-            break;
-        case 3:
-            //1.5 stop bits
-            charBits += 1.5f;
-            break;
-        default:
-            throw new ShouldNeverHappenException("Unknown stop bit size: " + wrapper.getStopBits());
+            case 1:
+                //Strangely this results in 0 stop bits.. in JSSC code
+                break;
+            case 2:
+                charBits += 2f;
+                break;
+            case 3:
+                //1.5 stop bits
+                charBits += 1.5f;
+                break;
+            default:
+                throw new ShouldNeverHappenException("Unknown stop bit size: " + wrapper.getStopBits());
         }
 
         if (wrapper.getParity() > 0)

src/com/serotonin/modbus4j/sero/messaging/EpollStreamTransport.java

@@ -4,8 +4,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 
-import com.serotonin.modbus4j.sero.epoll.Modbus4JInputStreamCallback;
 import com.serotonin.modbus4j.sero.epoll.InputStreamEPollWrapper;
+import com.serotonin.modbus4j.sero.epoll.Modbus4JInputStreamCallback;
 
 /**
  * First, instatiate with the streams and epoll. Then add a data consumer, or create a message control and pass this as
@@ -34,20 +34,25 @@ public class EpollStreamTransport implements Transport {
     }
 
     /** {@inheritDoc} */
+    @Override
     public void setConsumer(final DataConsumer consumer) {
         epoll.add(in, new Modbus4JInputStreamCallback() {
+            @Override
             public void terminated() {
                 removeConsumer();
             }
 
+            @Override
             public void ioException(IOException e) {
                 consumer.handleIOException(e);
             }
 
+            @Override
             public void input(byte[] buf, int len) {
                 consumer.data(buf, len);
             }
 
+            @Override
             public void closed() {
                 removeConsumer();
             }
@@ -57,6 +62,7 @@ public class EpollStreamTransport implements Transport {
     /**
      * <p>removeConsumer.</p>
      */
+    @Override
     public void removeConsumer() {
         epoll.remove(in);
     }
@@ -67,12 +73,14 @@ public class EpollStreamTransport implements Transport {
      * @param data an array of {@link byte} objects.
      * @throws java.io.IOException if any.
      */
+    @Override
     public void write(byte[] data) throws IOException {
         out.write(data);
         out.flush();
     }
 
     /** {@inheritDoc} */
+    @Override
     public void write(byte[] data, int len) throws IOException {
         out.write(data, 0, len);
         out.flush();