Modbus TCP经常出现读不到数据的问题

[hidafa]

服务器是正常的，但Modbus TCP经常出现读不到数据的问题。
麻烦大家看看这个类是不是有问题？
另外哪位有稳定的Modbus TCP通讯类，提高一下，谢谢。
谢谢。

package net.wimpi.modbus.facade;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class ModbusConnect {
	  //instance attributes
	  private Socket m_Socket;
	  private int m_Timeout = ModbusTCPMaster.TIMEOUT;
	  private boolean m_Connected;
	  private DataInputStream m_Input  = null;	  //input stream
	  private DataOutputStream m_Output  = null;	 //output stream
	  private InputStream m_InputStream   = null;    //wrap into filter input
	  private OutputStream m_OutputStream   = null;      //wrap into filter output
     
      
	  /**
	   * Constructs a <tt>TCPMasterConnection</tt> instance
	   * with a given destination address.
	   *
	   * @param adr the destination <tt>InetAddress</tt>.
	   */
	  public ModbusConnect() {
	  }//constructor

	  /**
	   * Opens this <tt>TCPMasterConnection</tt>.
	   *
	   * @throws Exception if there is a network failure.
	   */
	  public void connect(String IP)
	      throws Exception {
	    if(!m_Connected) {
	    	try{
	           m_Socket = new Socket(IP, 502);
	           m_Socket.setSoTimeout(1000);
	           new ModbusConnect().prepare();
	           m_Connected = true;
	      }catch (Exception e) {
			m_Connected = false;
		}
	    }
	  }//connect

	  /**
	   * Closes this <tt>TCPMasterConnection</tt>.
	   */
	  public void close() {
	    if(m_Connected) {
	      try {
			  m_InputStream.close();
			  m_OutputStream.close();
			  m_Output.close();
		      m_Input.close();
	        m_Socket.close();
	      } catch (IOException ex) {
	      }
	      m_Connected = false;
	    }
	  }//close


	  /**
	   * Returns the timeout for this <tt>TCPMasterConnection</tt>.
	   *
	   * @return the timeout as <tt>int</tt>.
	   */
	  public int getTimeout() {
	    return m_Timeout;
	  }//getTimeout

	  /**
	   * Sets the timeout for this <tt>TCPMasterConnection</tt>.
	   *
	   * @param timeout the timeout as <tt>int</tt>.
	   */
	  public void setTimeout(int timeout) {
	    m_Timeout = timeout;
	    try {
	      m_Socket.setSoTimeout(m_Timeout);
	    } catch (IOException ex) {
	      //handle?
	    }
	  }//setTimeout


	  /**
	   * Tests if this <tt>TCPMasterConnection</tt> is connected.
	   *
	   * @return <tt>true</tt> if connected, <tt>false</tt> otherwise.
	   */
	  public boolean isConnected() {
	    return m_Connected;
	  }//isConnected

	public Socket getM_Socket() {
		return m_Socket;
	}

	public void setM_Socket(Socket socket) {
		m_Socket = socket;
	}
	
	public void prepare() throws IOException{
		    if(m_Socket != null){
			    m_InputStream = m_Socket.getInputStream();
				m_OutputStream = m_Socket.getOutputStream();
	  			m_Output = new DataOutputStream(m_OutputStream);  
			    m_Input = new DataInputStream(m_InputStream );
					    	
		    }
	}
	
    public List read(int unitvar,int startAddress,int length,int number) throws UnknownHostException, IOException{
  		
    	List list = new ArrayList();
    	if(m_Output != null){
  			     synchronized (m_Output) {
  			    
  			    	int number1 = 0;
				    int number2 = 0;
				    if(number > 255 ){
					    number1 = number/256;
					    number2 = number - (number1*256);
				    }else{
					   number2 = number;
				    }
   			      int startAddress1 = 0;
  				  int startAddress2 = 0;
  				  if(startAddress > 255 ){
  					startAddress1 = startAddress/256;
  					startAddress2 = startAddress - (startAddress1*256);
  				  }else{
  					startAddress2 = startAddress;
  				  }
  				  byte[] b = new byte[12];
  				  b[0] = (byte)number1;
  				  b[1] = (byte)number2;
  				  
  				  b[2] = (byte)0;
  				  b[3] = (byte)0;
  				  
  				  b[4] = (byte)0;
  				  b[5] = (byte)6;
  				  
  				  b[6] = (byte)unitvar;
  				  b[7] = (byte)3;
  				  
  				  b[8] = (byte)startAddress1;
  				  b[9] = (byte)startAddress2;
  				  
	  			  b[10] = (byte)0;
	  			  b[11] = (byte)length;

  				  try{
  					  m_Output.write(b);
  				  }catch (Exception e) {
					// TODO: handle exception
  					  e.printStackTrace();
  					  close();
				  }
  				  m_Output.flush();
		          int  readBufferNumber = length*2 + 9;
		          byte[] readBuffer = new byte[readBufferNumber];   
		          

				    int nIndex = 0; 
				    int nTotalLen = readBuffer.length; 
				    int nReadLen = 0; 

				    try{
				    	while (nIndex < nTotalLen) 
				    	{ 
				    		nReadLen = m_Input.read(readBuffer, nIndex, nTotalLen - nIndex); 

				    		if (nReadLen > 0) 
				    		{ 
				    			nIndex = nIndex + nReadLen; 
				    		} 
				    		else 
				    		{ 
				    			break; 
				    		} 
				    	}

				    }catch (Exception e) {
				    	// TODO: handle exception
				    	Date date = new Date();
				    	java.sql.Date sqlDate = new java.sql.Date(date.getTime());
				    	java.sql.Time sqlTime = new java.sql.Time(date.getTime());
				    	String t = sqlDate.toString() + " " + sqlTime.toString();

				    	System.out.println("read error >>> Time:" + t
				    			                           + " IP:" + m_Socket.getRemoteSocketAddress()
                                                           + " unitvar:" + unitvar
                                                           + " startAddress:" + startAddress
                                                           + " length:" + length
                                                           + " number:" + number);
				    	e.printStackTrace();
				    	close();
				    }

		          
		          for (int i = 9; i < readBuffer.length; i++) {
					   Integer var = Byte.valueOf(readBuffer[i]).intValue();
					   if(var < 0) var = var + 256;
					   list.add(var);
				  }
				 	
		}				

    	 }
    	
    	return list;
      }

}