CrossLoop - based on TightVNC

CrossLoop is a FREE secure screen sharing utility designed for people of all technical skill levels. CrossLoop extends the boundaries of traditional screen sharing by enabling non-technical users to get connected from anywhere on the Internet in seconds without changing any firewall or router settings. It only takes a few minutes to setup and no signup is required.
CrossLoop screen sharing has countless remote applications:
  • Collaborate with a coworker in Word, Excel or Powerpoint or any other application
  • Troubleshoot difficult to describe computer problems for a family member
  • Talk on Skype with a friend while co-browsing the web
  • And many more...

  • All data sent between computers is encrypted using a strong 128-bit blowfish encryption algorithm.

    CrossLoop also uses the free, open-source VNC (Virtual Network Computing) viewer and server combination from TightVNC. CrossLoop makes it possible for TightVNC to operate when either or both of the computers are situated behind restrictive firewalls.

    Mrinal Desai says:
    "CrossLoop by itself is not opensource but tightVNC, what we use underneath, is. We packaged it with our code to make it really simple."
    "is powered by proprietary VIP Tunnel technology"
    "It is built on a P2P architecture and is available at"

    Wondering why I posted it here when CrossLoop is not open source? Well I wanted to write about TightVNC and ended up posting about CrossLoop. I mentioned about UltraVNC sometime back and talked about some of its features. The reason I have included CrossLoop here is because this will help us in some ways to appreciate the open source development sensibility and how it empowers others to think in different yet simpler ways. I will not talk about the pros or cons of CrossLoop because that is not something that will fit in here but definitely talk a bit about TightVNC which seems to have proved that it can be fit into any industry standard software so seamlessly thus not only empowering the person using it but also the idea behind having open source software in the first place. TightVNC is similar to RealVNC except that it is much more advanced and feature packed than RealVNC. A small introduction to TightVNC is available which describes in detail the amazing capabilities of TightVNC. No wonder we can expect it to be part of many more applications to come. I am watching out for some exciting options from DimDim which is part of this application space (collaboration, screen sharing etc...) and I can say from the way it looks it will be one more amazing initiative in the open source realm. More on DimDim in the future.

    Incase you are interested to know more about CrossLoop you may visit:
    Open Source, Innovation and Service - Story of Crossloop by Rajesh Shetty.

    Question to readers:
    Can open source and closed source applications complement each other ? Does CrossLoop based on TightVNC prove this?


    Anonymous said…
    I am Sundar and am part of Dimdim. If you are interested can we please schedule a call and it would be great to get feedback from you on Dimdim.
    Anonymous said…
    As far as your question at the end, I don't know. But if they are distributing the binaries of tightvnc they also need to provide the source. Since they aren't (don't see it on the download page) they're in violation of the gpl.
    Techknight said…
    But do you mean that they will have to make CrossLoop open source too? Or its just that will have to include the source of TightVNC along with their package. Sorry but I have never tried to understand the GPL very clearly. But maybe now I should. If indeed what you say is true then we can point it out at the right place early! - Thanks...
    Anonymous said…
    Crossloop violates clause 2.b of GPL.

    Their application cannot function without TightVNC, therefore it is a "derived work" as per GPL definition and consequently it must be distributed under GPL.

    The question is not *if* they violated GPL, the question is *when* they are going to face the problems because of that. And I wouldn't want to be their customer when they do.
    Techknight said…
    Hi.. to All Readers (of OSAFW),
    I have asked Mrinal (on behalf of CrossLoop) to reply us back and clarify this issue posted in the recent posts of it violating GPL.
    The link to the message left:

    Hope Mrinal replies to our request soon.
    Mrinal said…
    First, let us thank you for bringing the GPL issue to our attention Jyotirmoy. We had believed that we were in compliance with the TightVNC GNU GPL because we were re-distributing unmodified TightVNC binary code from the website. We thought that since the source code of TightVNC was available on that website that we did not need to post the same source code on our website. We were mistaken in our interpretation of the GPL and have corrected the situation by posting both the binary and source code of TightVNC on our website.

    Please see, This page can be reached from a link at the footer of the website labeled "TightVNC-GPL". We also expect to add a link to this page from our FAQs.

    I hope this addresses your question and again - thanks for helping us learn!

    If you or any of your readers have questions, you can contact me anytime and you are welcome to share my information with them!
    Techknight said…
    Hi Mrinal,
    Thanks to you and Tom for being patient with me and making it clear to me that CrossLoop does not violate the GNU GPL. Its clear from what you have told me and what you have done that CrossLoop has taken all steps to ensure that it adheres and supports the GNU GPL and mostly TightVNC.
    Regarding the query about GPL Section 2 being not met here is Tom's clarification which diffuses the cloud of uncertainty over us about CrossLoop.
    Section 2. of the GNU GPL, which you included in your email, does not apply to CrossLoop. The reason is that we do not modify the GNU GPL program. Only Section 1. of the GNU GPL applies to CrossLoop because we distribute an unmodified copy of TightVNC.

    You can prove this to yourself with the following steps:

    1) Install CrossLoop on a Windows computer
    2) Go to the default CrossLoop installation directory:
    C:\Program Files\CrossLoop
    3) In that directory you will find the following files:
    - vncviewer.exe
    - winvnc.exe
    - VNCHooks.dll
    as well as a copy of the GNU GPL license in:
    - gpl.txt
    4) Verify that we have not modified a single byte of TightVNC by comparing each of the files.
    To do this you can use a Command Prompt window and the FC program to compare the files.

    To demonstrate:
    - go to
    - download
    - create a directory under CrossLoop
    C:\Program Files\CrossLoop\Original
    - extract the ZIP file into
    C:\Program Files\CrossLoop\Original
    - open a Command Prompt window and navigate to the directory you created
    c:\>cd "C:\Program Files\CrossLoop\Original"
    - use the FC command to compare the binaries:
    C:\Program Files\CrossLoop\original>fc vncviewer.exe ..\vncviewer.exe
    Comparing files vncviewer.exe and ..\VNCVIEWER.EXE
    FC: no differences encountered

    C:\Program Files\CrossLoop\original>fc winvnc.exe ..\winvnc.exe
    Comparing files winvnc.exe and ..\WINVNC.EXE
    FC: no differences encountered

    C:\Program Files\CrossLoop\original>fc VNCHooks.dll ..\VNCHooks.dll
    Comparing files VNCHooks.dll and ..\VNCHOOKS.DLL
    FC: no differences encountered

    The above steps should prove to you that we have not modified a copy of TightVNC and are thus fully compliant with section 1. of the GNU GPL.
    Section 2. of the GNU GPL does not apply to CrossLoop.

    The CrossLoop core technology runs entirely without any VNC modifications. CrossLoop can also run with several other unmodified VNC versions, such as: RealVNC, UltraVNC and TridiaVNC to name a few that we have tested. It is our conclusion that TightVNC is the best choice for our application.

    The last line by Tom which talks about TightVNC being the best choice also proves beyond doubt that the developers of CrossLoop will not shy away from their appreciation for TightVNC.

    Thanks again Tom and Mrinal from CrossLoop to clear our doubts. All the best to you and your team.
    Anonymous said…
    GPL is far more complex license that it appears to be on the surface.

    Crossloop violates GPL.

    See this GPL FAQ entry that deals EXACTLY with this situation:

    In particular this section:

    "To do this validly, you must make sure that the free and non-free programs communicate at arms length, that they are not combined in a way that would make them effectively a single program."

    Crossloop is "a work based on the Program" regardless of whether they modify TightVNC sources or not. It does not work without TightVNC and therefore they are EFFECTIVELY one program as far as GPL is concerned.

    GPL has been around for little under 20 years. It was written by a free software activists, who also happen to be software developers. It's an extremists license. What touches GPL becomes GPL. There are NO loopholes in GPL, not to mention so obvious one that Crossloop is trying to bet on.
    Tom Rolander said…
    The purpose of this post is to refer your readers to an updated page on our website which is devoted to the issue of the GPL-covered TightVNC. There is a link to this page from the footer of every page on the CrossLoop website.

    In addition to fully describing the relationship between the CrossLoop shell program and TightVNC, we have added an FAQ section on our VNC page to address the issues raised on your blog.

    CrossLoop is a proprietary shell program which uses the VIP Tunnel to negotiate a connection between two peer computers. After approval has been obtained from the HOST computer to accept a connection request from the JOIN computer, an encrypted and secure connection is established between the two peer computers using the VIP Tunnel. At that point, the CrossLoop shell program invokes the plug-in program which is specified in a companion XML shell script file. In the case of CrossLoop for Windows as it is currently released (Beta Version 1.0 Build 20061101161100), the CrossLoop shell uses fork and exec to invoke the TightVNC plug-in program.

    It is important to note that the CrossLoop shell program has no internal dependencies on VNC. To illustrate this point there are several other applications which use the CrossLoop shell and the VIP Tunnel and do not include VNC. Two of the programs are: Access My Files, a simple solution to remote file access (; and Remote Desktop Search, a free service that makes it possible to remotely access all of the information indexed by your Google Desktop anywhere in the world, (

    In essence, the CrossLoop shell and VIP Tunnel enable the VNC to perform screen sharing between two computers on separate networks through firewalls. The identical function could also be provided by a VPN connection between the two computers on separate networks using the same GPL-covered VNC program. CrossLoop enables VNC, or other client/server applications, to operate in the absence of VPN.

    We believe that CrossLoop fully complies with the terms of the GPL. Our FREE product improves the quality of the VNC experience by enabling VNC to operate through firewalls. In the near future we will offer more CrossLoop solutions which enable client/server applications to operate through firewalls.
    Techknight said…
    Thanks Tom. I am sure we will have some pointers in the right direction very soon from the readers of this post.
    josh said…
    Those are very good tools, however, in many cases those platforms are used just to allow the team to review the same document together in real-time and "be on the same page".
    The recently launched free site does exactly that, quickly show documents to friends and colleagues.
    It allows Free Web meeting and co-browsing on any document, user uploads a document and invites friends to view it with him live
    All the participants in the session see each others' drawing, highlights, etc.


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