SocketChannel Client not reading Messages sent by Server and drop of message

[Karthik Rajendiran]

Dear Team,

We have a application which is socketChannel Client connects to the server with a single connection. Sending the ISO Transaction request to the server.
Client sends Echo messages at freq interval to the ISO Switch, similarly Server can also send Echo Requests to the client.

In production, we could see lot of messages are not read by client , but in TCPDUMP, it shows server sent the rquest and reached the client.

We have a problem related to packets getting not read by a socketchannel client, where as server responded back to us with response

Please find the code for the socketchannel read [ We are using Blocking Mode]. Kindly suggest the way to tune the code.

public static synchronized String readSysMessageSize(SocketChannel sock) throws Exception 
	{
		ByteBuffer buffer = null;// ByteBuffer.allocateDirect(9216);
    	CharBuffer charBuffer = null;//CharBuffer.allocate(9216);
    	Charset charset = Charset.forName("ISO-8859-1");
		CharsetDecoder decoder = charset.newDecoder();
		
		String stResponse = "";
		String stResponse1 = "";
		try
		{
//			logger.info("SysMessageReceiver:readSysMessage:Entered:");
			//if(true)
			
			{
				stResponse="";
				//read length 
				buffer= ByteBuffer.allocateDirect(2);
				charBuffer = CharBuffer.allocate(2);
				if ((sock.read(buffer)) != -1) 
				{
					buffer.flip();
					decoder.decode(buffer, charBuffer, false);
					charBuffer.flip();
					stResponse = charBuffer.toString();
					try
					{
						buffer.clear();
						decoder.flush(charBuffer);
						buffer.flip();
						charBuffer.clear();
						charBuffer.flip();
					}
					catch(Exception e)
					{
						
					}
				}
				//calculate length
				String hexa="",stLength=stResponse;
				for(int i=0;i<2;i++)
				{
					int inDeci = (int)stLength.charAt(i);//to convert char to deci
					hexa =hexa+IBSUtils.formMessageElement((Integer.toHexString(inDeci)) + "", 2, '0', 'L');// to convert deci to hex
//					hexa = hexa+Integer.toHexString(inDeci);// to convert deci to hex
					logger.info(stLength.charAt(i)+":"+ inDeci +":"+hexa);
				}
//				System.out.println("Hexa Value of the Length:"+hexa);
				int inreslength = Integer.valueOf(hexa, 16).intValue();//to convet hex to deci
				//read data
				buffer= ByteBuffer.allocateDirect(inreslength);
				charBuffer = CharBuffer.allocate(inreslength);
				if ((sock.read(buffer)) != -1) 
				{
					buffer.flip();
					decoder.decode(buffer, charBuffer, false);
					charBuffer.flip();
					stResponse = charBuffer.toString();
					try
					{
						buffer.clear();
						decoder.flush(charBuffer);
						buffer.flip();
						charBuffer.clear();
						charBuffer.flip();
					}
					catch(Exception e)
					{
						
					}
				}
				stResponse=stLength+stResponse;
			}
			//else
			{
//				logger.info("No Data to Read/Receive");
			}
		}
		catch(java.net.SocketTimeoutException socketTimedOutExceptionObj)
		{
			logger.error("Timed Out"+socketTimedOutExceptionObj);
			stResponse = "T";
		}
		catch(ConnectException connException)
		{
			logger.error("SysMessageReceiver:Connection Exception:connException:1"+connException);
			throw connException;
		}
		catch(IOException ioException)
		{
			logger.error("SysMessageReceiver:Connection Exception:ioException:2"+ioException);
			throw ioException;
		}
		catch(Exception exceptionObject)
		{
			logger.error("SysMessageReceiver:Connection Exception:exceptionObject:3"+exceptionObject);
			throw exceptionObject;
		}
		finally
		{
			charset = null;
			if(decoder!=null)
			{
				decoder.reset();
				decoder = null;
			}
			if(charBuffer!=null)
			{
				charBuffer.clear();
				charBuffer.flip();
				charBuffer = null;
			}
			if(buffer!=null)
			{
				buffer.clear();
				buffer.flip();
				buffer = null;
			}
		}
//		logger.info("SysMessageReceiver:readSysMessage:Exited:"+stResponse+":");
		logger.info("Exit:readSysMessage:(S):stResponse:Length:"+stResponse.length());
		return stResponse;
	}