Bridge Between Java And Windows

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Introduction

I have included some code that can make your windows programs and your java programs communicate with each other easily.  The emphasis is on the word easily, because there could be a lot of different ways to do the same thing.  On the windows side, I wrote an ActiveX control called XYMessenger.  On the java side, I wrote a java class also named XYMessenger.  These two components have almost identical methods and they can send each other messages of arbitrary size.  If the word XYMessenger sounds familiar to you that is because I previously posted an article on CodeProject about a client-server development tool package I wrote.  The package is now free (for commercial or non-commercial use) but the source code is not provided to the public at this time.  The code provided here are simplified versions of the key components in that package.  You can use and modify the code anyway you wish if you acknowledge in your work that the original idea is from me :-).

The Ideas

The basic idea is, if you insert the XYMessenger.ocx control into your VB or MFC program or other windows program that can use an ActiveX control, then your program can act as both client or server to other programs also using XYMessenger.  For your java programs, you need only to derive a class from the XYMessenger to achieve the same goal.  A call to the ConnectDirect method is all you need to join the communication.  The first program to call ConnectDirect will be acting as the root node in a tree called the communication tree.  The root node needs to use a local port for other programs to connect to.  Other programs will connect to this root node using the ip address and the port number (of the root node).  These programs will be the clients to the root node, however, each of them can also be a server so that more and more programs can be connected together.

What can you do once you connected your programs together?  Well, the SendTextMsg method allows you to send messages of arbitrary size to other connected programs.  How do you know who to send the message to?  Each node in the communication tree is identified by a user identifier of the form Name@XXX, where Name is the login name used in the call to ConnectDirect and XXX is a digit string dynamically generated by the system to identify the position of the node in the communication tree.  The GetUserCount and GetUser methods can be used to retrieve user identifiers of all nodes.  For example, GetUser(0) will return the user identifier of the first user in the internal user list, GetUser(-1) will return the user identifier of the current node.  GetParent will return the user identifier of the parent node of the current node.

What does a message look like?  A message has the following attributes:  Sender (user identifier), Receiver (user identifier), MsgID (integer), SenderMsgID (integer), Title, Text, and AppSpecificCode (integer).  The Sender, Receiver, Title, and Text fields are null terminated character strings in windows programs, and they are byte arrays in java programs.

Where are incoming messages stored and how to retrieve and process them?  The incoming messages are stored in an internal message array.  For windows programs, an ActiveX event will be fired when a new message arrives, the developer is supposed to implement an event handler and process the message there.  For java programs, the developer is supposed to override the virtual message handler function in the base class XYMessenger to process the message.  In both cases the message handlers will be invoked by the system automatically.  The GetMsgCount method returns the total number of messages in the internal message array.  There is an nMsgID parameter in the message handler, you can use it to call the GetMsgIndex method to obtain an index of the message.  This returned index can be used to call GetMstTitle, GetMsgText, GetMsgAppSpecificCode, etc.  The RemoveMsg method destroys the message with given index.

The SendSyncTextMsg method is used to send a synchronous message to a node.  It will not return until the receiver has sent a reply message or time-out occurs.  You can specify the time-out value (in seconds) with this method.  The method returns a positive integer which can be used to call GetMsgIndexWithSenderMsgID to obtain the index of the reply message.  If the receiver does not reply or the method fails, then the return value will be -1.  By the way, the message sent by SendSyncTextMsg has to be replied by calling the ReplySyncTextMsg method using the nSenderMsgID parameter of the original message as the first parameter in the call. Please also note that the user implemented message handler will be called before SendSyncTextMsg returns. If you delete all incoming messages from within the handler, SendSyncTextMsg will return -1 as if the receiver never replied to the sent message.

What if the data I want to send contains embedded null characters (such a .exe file)?  Well, there is never a problem if you only use the java component.  For consistency, I wrote two functions, ReplaceNull and RestoreNull in both java and c++, that can be used to remove null characters from data before sending the message and restore the null characters after receiving the message.  The java version is in class XYAPI, the c++ version is in file XYStatic.cpp.

I am very confident that the code and the basic ideas can be very useful in general client-server programming, not just being a bridge between java and windows programs.  In fact, I have built pretty complicated server programs and have used XYMessenger in both web clients (embedding XYMessenger in applet) and web servers easily.  Please check my web page for details.

How To Use The Sample Programs

For your convenience I have included the binary code in the zip file (the code size is extremely small).  Here are the steps to install:

• Unzip the downloaded file.
• Register XYMessenger.ocx
• Include the full path of the XYMessenger.jar file into your CLASSPATH environment.

The java sample program is implemented in the class XYTester.  This program tries to send a message to each connected node and then broadcast a message to all nodes every 3 seconds.  You can run multiple instances of this program.  The command line to start the program is:

java XYTester  ServerAddress  ServerPort  LocalPort

Note that if ServerPort is 0, then the instance will be the root node.  If LocalPort is 0, then the instance can only be a client (not accepting any connections).  Here is an example on using this program:

• First start the root node with the following command:  java  XYTester  ""  0  5000
• Then start one or more clients with the command:  java  XYTester  ""  5000  0
• Then start another client which is also a server with the command:  java  XYTester  ""  5000  5001
• Then start one or more clients of the above client with the command:  java  XYTester ""  5001  0

Note that if the instances of XYTester are running on different machines, then the "" string should be replaced by server address (the name of the server machine or its ip address).

The windows sample program is called XYTreeDemo.  It is a dialog based program.  Like XYTester, you can use multiple instances of XYTreeDemo to build the communication tree.  However, this program has the capability of building multiple communication trees within a single process.  If you start the program and click the Create Node button, then a separate user interface thread will be created with an instance of XYMessenger embedded in a new dialog.  The Connect button on the new dialog will call the ConnectDirect method to create a new node in a communication tree.  This new node can be a client or a server (or both).  After successfully connected, the Send button will, of course, send a message to another node.  You can click the Create Node button on the main dialog to create as many nodes as possible.

Now the fun part, see what happens if you connect an instance of XYTreeDemo to an instance of XYTester, or connect an instance of XYTester to an instance of XYTreeDemo.

The Implementation

The ActiveX control XYMessenger.ocx is implemented with VC++ 5.0 using the CSocket class of MFC.  The java class XYMessenger is implemented with JDK 1.2.2 using the Socket and ServerSocket classes of java.net.

Each instance of XYMessenger.ocx can only be used in a single thread (apartment model threading).  As demonstrated by the XYTreeDemo program, you can use multiple instances of XYMessenger.ocx in multiple threads.  There is nothing to prevent you from using multiple instances of XYMessenger.ocx in a single thread.  Even if an instance of XYMessenger.ocx is waiting for a reply message from another node, the thread is not blocked, it can still process incoming messages from other nodes.

The java class XYMessenger is truly multi-threaded in the sense that each connection (between two nodes) is running in a separate thread.  Therefore, the user implemented event handlers (virtual functions) have to be thread-safe even if you use only one instance of XYMessenger.

The Limitations

The simplified code provided here has a hard coded limit of connecting at most 10 clients to a server (however, each of the 10 clients can have 10 clients connected to it).  It is not hard to increase the limit to, say 1000.  Another limitation is, each node in the communication tree maintains a list of user identifiers of all nodes.  This can be inefficient if there are hundreds of nodes connected together.  The free package on my web page does not have these limitations, of course, and it has a lot more functionality besides simply connecting programs together.

Thank you for reading this article.  Your input is appreciated.

Updates

14 June 2002

• Fixed a bug in both the java and the ocx version of XYMessenger.
• Modified code so that XYMessenger.ocx can now be used in console applications.
• Added a simple console demo program.
• The unicode version of XYMessenger.ocx is fixed. But it is not yet compatible with the java XYMessenger class.

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Instructions to run the project? codeprojuser 0:18 3 Apr '08   We have downloaded the BridgeWinJava-1.zip to the local machine. we did the following steps: 1.Unzip the downloaded file. 2.Register XYMessenger.ocx 3.Include the full path of the XYMessenger.jar file into your CLASSPATH environment. We tried running the java file XYTester.java. (using the values given in the site for ServerAddress,ServerPort n LocalPort). [Working\XYMessengerJava>java XYTester "" 0 5000 Connected ] It showed connected Can we have the steps to run the program and see it working? Thanks. Sign In·View Thread·PermaLink 2.00/5 (2 votes) when to call remove message testing testing 14:10 15 Dec '07   SHould I call remove Message? The XY TRee doesn't call this at all. Who should be responsible to remove broadcast message, any help will be greatly appreciated. Sign In·View Thread·PermaLink .ocx singhswat 0:12 5 Jan '07   hi everybody, I want to use a ocx in my java application. can anybody provide me a sample code snippet of how to do it............ please... regards swat Sign In·View Thread·PermaLink Recompiled .ocx in win2k Jian1234567 5:08 1 Jul '05   Hi, if the source for XYMessenger.ocx was recompiled with VS6 sp5 in win2k, the new .ocx does not work with Java. But the original .ocx is fine. Can you tell me what environment you used when you built it? Thanks, Jian Sign In·View Thread·PermaLink 2.00/5 (1 vote) Recompiled .ocx in win2k3 Jian1234567 10:08 30 Jun '05   When I recompiled .ocx with VS6.0 SP5 in win2k3 server, the .ocx does not work. Here is error message: E:\BridgeWinJava\Working\XYMessengerJava>java XYTester "" 5000 0 User login: Tester/ Error 6, Connection to server closed Error 11, Exception in XYMessenger.BroadcastTextMsg: Socket closed Failed to connect If I used your compiled .ocx, it works well. Any ideas? Thanks, Jian Sign In·View Thread·PermaLink problem using xymessenger.cpp/h Anonymous 11:54 25 Mar '05   Hi, I try to integrate XYMessenger in my MFC DLL. For that purpose I just integrated in my project the following files using VC++ 6.0 : /********************/ xymessenger.cpp xymessenger.h ressource.h nwsapi.lib /*********************/ I declare in my header file : /*****************************/ CXYMessenger m_xymessenger; /****************************/ and in my cpp I try to use the commande: /**************************************/ LPCTSTR strUserName = _T("test"); LPCTSTR strPassword = _T("test"); LPCTSTR strServerAddress = _T(""); long nServerPort = 0; long nLocalPort = 4000; long nTimeout = 16; m_xymessenger.ConnectDirect(strUserName,strPassword,strServerAddress,nServerPort,nLocalPort,16); /**************************************/ Once I reach this command : m_xymessenger.ConnectDirect(...) I obtain the following error message: /**************************************/ Debug Assertion Failed ! Program:........ File: winocc.cpp line: 345 etc. /***************************************/ Do you have any idea about what I could do wrong ? Thanks a lot Sign In·View Thread·PermaLink Re: problem using xymessenger.cpp/h Xiangyang Liu 1:24 26 Mar '05   XYMessenger is an Active X control that uses MFC. You can easily use it in your own dlls or exes. However, you cannot simply take the serouce code and compile them into your own projects. It requires a lot knowledge and effort to do that, and it is probably not worth the time. If you want a new feature, you can modify the XYMessenger component itself. Integrating with your own project at the source level is hard and not very useful in my opinion. Good luck. My articles and software tools Sign In·View Thread·PermaLink 2.00/5 (1 vote) XYTreeDemo failed to connect Anonymous 13:40 23 Mar '05   The result is the same, if I try to run first XYTreeDemo as a server, ie, Server Port : 0, Local Port : 5000 and click connect I will have this message: "Error: Failed to create socket." "Failed to connect" I only filled up the user name and password by "Test" and of course Server Port with "0" and Local Port with "5000". Do I really need to fill up the other topics, like "Msg Destination" and "AppSpecificCode" ? If yes with what String ? Thanks a lot for your help Sign In·View Thread·PermaLink Re: XYTreeDemo failed to connect Xiangyang Liu 14:33 23 Mar '05   I think you may be starting two instances of the server using the same port (5000). Please try the following, do exactly as I said here: 1. Exit from all instances of XYTreeDemo. 2. Start a new instance of XYTreeDemo. 3. Click the "create node" button to start a server node, enter the following and click "connect" button: User Name: test1 Password: test1 Server Port: 0 Local Port: 4000 4. Click the "create node" button again to start a client node, enter the following and click the "connect" button: User Name: test2 Password: test2 Server Port: 4000 Local Port: 0 Please note that the port numbers here are different from the server node instance. 5. If everything works fine so far, you can start sending messages from the server to the client or from the client to the server. Good luck. My articles and software tools Sign In·View Thread·PermaLink Re: XYTreeDemo success to connect Anonymous 13:26 24 Mar '05   it works great by following the right order, thanks a lot this is a very nice tool !!! Sign In·View Thread·PermaLink XYTreeDemo Failed to connect angel420 19:55 21 Mar '05   Hi, I just downloaded XYTreeDemo, compiled it under VC++ 6.0 and execute it: I put these parameter: Login Name: "Test" Password : "Test" Server Port : 5000 Local Port : 0 I also registered the XYMessenger.OCX on my computer correctly. In the application, when I click "connect" I have this message after the time out: "Failed to connect" "Error: Connect failed" Why ? Thanks for your help Sign In·View Thread·PermaLink Re: XYTreeDemo Failed to connect Xiangyang Liu 6:21 22 Mar '05   It failed because you were running a client without a server. 1. First, run XYTreeDemo as a server, this requires the following parameters in addition to others: Server Port : 0 Local Port : 5000 2. Then, run XYTreeDemo as a client, you can use the following parameters: Server Port : 5000 Local Port : 0 Note: the client and the server can be on the same machine and they can be in the same process, too. Good luck. Sign In·View Thread·PermaLink Re: XYTreeDemo Failed to connect Anonymous 12:40 22 Mar '05   The result is the same, if I try to run first XYTreeDemo as a server, ie, Server Port : 0, Local Port : 5000 and click connect I will have this message: "Error: Failed to create socket." "Failed to connect" I only filled up the user name and password by "Test" and of course Server Port with "0" and Local Port with "5000". Do I really need to fill up the other topics, like "Msg Destination" and "AppSpecificCode" ? If yes with what String ? Thanks a lot for your help Sign In·View Thread·PermaLink COM-Java integration scenario esordini 1:28 3 Sep '04   Hi, first off, let me congratulate you on your fine work. Then, I would like to pose a question about a problem I'm faced with, to see your package could be of any help to me. The aim here is to make a Java program of mine implement a given COM interface, whose set of methods and properties is defined by a spec. So, an incoming method call to a COM method from a client should trigger the following chain of events: 1) The incoming call is received from the client, with its parameters; 2) The call is forwarded to the Java program, which processes the parameters and gives the output, if any; 3) The bridge gets the response data and sends them back to the COM client, thereby terminating the call. Other requirements/facts: 1) As you can see from the above description, the client is a C++ program, and the server is a Java app; 2) Most (if not all) calls are plain synchronous method invocations; 3) The communication model is of the peer-to-peer kind, i.e. there can be only one client per server. 4) The bridging between the COM client and the Java server should preferably be done at "library level", thereby not calling for a third executable to be launched. However, this requirement is not mandatory. Any suggestions? Thanks in advance, Emmanuele Sordini Sign In·View Thread·PermaLink Re: COM-Java integration scenario Xiangyang Liu 2:53 3 Sep '04   There are more than one way to do this. Here is a simple way. 1. Your java program is the server which does the actual work. You can use an XYMessenger object (java version) in this program to process messages from the clients. 2. You c++ program is the client. It loads a com object (could be an ActiveX control, see step 3) and call its method. 3. The com object could be implemented in a dll or a ocx. It has the methods you want to call from your c++ program. When a com method is called, it will instantiate an XYMessenger object (ocx) and send the parameters to the java server. The java server will do the processing and send back the result. The com object will return the result back to your c++ program. You said there is only one client per server, but the above method does not prevent you from having more than one client per server. Also, you don't have to use XYMessenger if you want to build your own component or use a third party tool. Good luck. My articles and software tools Sign In·View Thread·PermaLink Re: COM-Java integration scenario esordini 8:40 5 Sep '04   Xiangyang Liu wrote: 2. You c++ program is the client. It loads a com object (could be an ActiveX control, see step 3) and call its method. Thanks for your reply. This scenario features three actors: 1) The real COM client, which I don't have any control over (it can even be a commercial product) 2) My Java-COM bridge, which is COM server to the above client and client to the Java program 3) My Java program: here is where your XYMessenger could come in handy. I've been experimenting with a C++ "bridge" prototype project, but I wasn't even able to register it as a COM object. I followed all the enclosed instructions, but nothing worked. Here comes the question: could your XYMessenger also be used with Visual Basic? I know, it's awful, but it looks like implementing the bridge in VB is way easier. Thanks, Emmanuele Sign In·View Thread·PermaLink Re: COM-Java integration scenario Xiangyang Liu 9:16 5 Sep '04   esordini wrote: I've been experimenting with a C++ "bridge" prototype project, but I wasn't even able to register it as a COM object. I followed all the enclosed instructions, but nothing worked. I think the difficulty lies in your skill level with COM programming (in C++). COM is very powerful, however it is also very complicated, you need to be familiar with certain existing libraries such as MFC and ATL to be able to write code quickly. esordini wrote: Here comes the question: could your XYMessenger also be used with Visual Basic? I know, it's awful, but it looks like implementing the bridge in VB is way easier. Yes, you can use XYMessenger in VB programs. It is an ActiveX control, using XYMessenger is no different from using other ActiveX controls as far as VB program is concerned. No, it is not awful, it is something real programmers have to do everyday on their jobs. Good luck. My articles and software tools Sign In·View Thread·PermaLink Re: COM-Java integration scenario esordini 22:32 5 Sep '04   Xiangyang Liu wrote: I think the difficulty lies in your skill level with COM programming (in C++). COM is very powerful, however it is also very complicated, you need to be familiar with certain existing libraries such as MFC and ATL to be able to write code quickly. You are right: I am a SW developer by trade, but my background is 80% Unix. I know MFC, but I've never used COM before. Xiangyang Liu wrote: Yes, you can use XYMessenger in VB programs. It is an ActiveX control, using XYMessenger is no different from using other ActiveX controls as far as VB program is concerned. Thanks: it's just what I needed to know. Xiangyang Liu wrote: No, it is not awful, it is something real programmers have to do everyday on their jobs. I know Thanks for your answer, I'll let you know. Best regards, Emmanuele Sign In·View Thread·PermaLink can i use jmf classes and interfaces...... Anonymous 22:59 9 Feb '04   can i use jmf player (jmf classes)...in VBA??? using XYMessenger.ocx...urgent and important...help... Sign In·View Thread·PermaLink Re: can i use jmf classes and interfaces...... Xiangyang Liu 2:23 10 Feb '04   I am not familiar with jmf classes, may be someone else can help you. Sorry. My articles and software tools Sign In·View Thread·PermaLink Passing simple message from Java to C# Filip Verhaeghe 22:44 20 Jan '04   Hello, I would like to do some simple message passing from Java to C#. I have a Java process that I want to monitor from C#. I have control over the source code of both sides. Essentially, all I want to do is transfer a string from Java to C#, one-to-one. Other types to exchange that would be useful are timestamps and long integers. I was wondering if you had done any experiments with this, and if you had sample code that sent a string or integer in Java and received it in C#? Thanks, Filip. Sign In·View Thread·PermaLink Re: Passing simple message from Java to C# Xiangyang Liu 4:48 21 Jan '04   Filip Verhaeghe wrote: I would like to do some simple message passing from Java to C#. You can use com component in .NET programs. If you don't want to write new code for communication, just use the XYMessenger.ocx control in your C# program. All you have to do is "add reference", .NET will generate a wrapper dll which has all the methods of XYMessenger. In your java code, you can use the XYMessenger class, and then, connect your C# and java programs and send messages between them. Good luck. My articles and software tools Sign In·View Thread·PermaLink Re: Passing simple message from Java to C# Filip Verhaeghe 8:29 21 Jan '04   Xiangyang Liu wrote: You can use com component in .NET programs. I know, and I have used this in the past, but I was hoping for a more specific code sample, which would reduce my work to cut, paste and adapt. Anyway, I am pretty sure that the value of XYMessenger to link Java to C# in a simple way is underrated. This type of connectivity is heavily in demand. It seems to me that an article on this topic would benefit the world... But I won't hold my breath, and start experimenting myself. Thanks for the tool. Sign In·View Thread·PermaLink Hello i have two questions on your article Bridge Between Java And Windows ponraj 4:06 13 Oct '03   Firstly, we have executed the XYTester class,we couldn't understand the imnplementation logic,how the bridge between the java code and the XYMessenger.ocx happens in the code.Explain the implementation logic of this bridge. Secondly, We want to integrate an MPEG player plays both AUDIO and VIDEO live Streams ,which contains an OCX File named "OptbasePlayerAx.ocx,in to our java application,for that we need some referrences either code or some documetation can you provide us? Sign In·View Thread·PermaLink Re: Hello i have two questions on your article Bridge Between Java And Windows Xiangyang Liu 7:42 13 Oct '03   ponraj wrote: Firstly, we have executed the XYTester class,we couldn't understand the imnplementation logic,how the bridge between the java code and the XYMessenger.ocx happens in the code.Explain the implementation logic of this bridge. The java code and the ActiveX control communicate via TCP socket connection. ponraj wrote: Secondly, We want to integrate an MPEG player plays both AUDIO and VIDEO live Streams ,which contains an OCX File named "OptbasePlayerAx.ocx,in to our java application,for that we need some referrences either code or some documetation can you provide us? Source code is included with this article. You need to download it to your machine by clicking the link at the top of the article. My articles and software tools Sign In·View Thread·PermaLink 1.00/5 (1 vote)

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