Learn how to a build a cloud-first strategyRegister Now

  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 303
  • Last Modified:

2-in-1 problem: Stream access and access violation


I'm trying to write a HTTP tunnel. My idea is to let a browser connect to a blocking serversocket, and administrate all data from the browser to the host in the thread, that is beeing spawned.

In the thread, I create a new TThread. This thread will then manage all responses from the proxy/HTTP server back to the browser.

In the TServerClientThread I create a new blocking socket (to connect to the HTTP/proxy server), but sometimes i get an access violation the setting Active:=True. Why?

Error is: Project nnnn raised exception class EAccessViolation with message 'Access Violation at address C000013C. Read of address C000013C'. ...

I also get '... 'Access Violation at address 00000000. Read of address 00000000'. ...

In the TServerClientThread I also create two WinSocketStream. One is beeing read from the TServerClientThread (HTTP requests) and written from the TThread (Answers from the HTTP/proxy server), and the other Stream works the otherway around.

Is this ok to do, without making any kind of mutual exclution? If not - how should this be done?
(I have not had any errors so far, but ...)

Hope to hear from you soon guys!


BTW: If anybody has some Delphi sourcecode for a network tunnel, I would really appreciate it.
1 Solution
As for Q1: Most likely the object has not been created, or it has been freed...


I suggest you take a look at the winshoes components.
They have the components you need :
tunnel master, and tunnel slave. they
is also a demo that show how to use things.
Get them on http://www.pbe.com/Winshoes
it's free and open source...

Let me know, if they is a problem...

I have done something similar to what you want, but i found it was easier to use NonBlocking.
Regarding Q1 : I'm using TServerSocket (NonBlocking) and i remember that some "socket.close" commands actually close all open treads. Maybe something similar happen in your program.

Good luck
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

jpvjAuthor Commented:
To Jeurk:

Hi again!

The Winshoes package looks very impressing, except for the (lack of) documentation!

Could you please explain, how the tunnel demo works?

Thanks in advance!

listening :-)
Where is a lack documentation ? ;)
ok. I agree.
This so well written that you don't need documentation.
You was trying to do some tunneling stuff, so you should understand what is going on ? no ?
To make the demo work : launch the server...
he will start to listen on host port 21.

After that, start a client, change th ip to, start it. The serveur will show you a connexion.
You cannot start more then on client on the same machine.

This how to do it the hard way. If you look at the components, you will see that they is a TMasterTunnel and a TSlaveTunnel.
They encapsulate all the fonctions you need...
jpvjAuthor Commented:
Hi Again!

Sorry for the long delay, but ... :-)

If have use the WinshoeMappedPort instead, and it work fine!

Thanks for your help!

jpvjAuthor Commented:
Comment accepted as answer
Glad I could help.

Featured Post

Vote for the Most Valuable Expert

It’s time to recognize experts that go above and beyond with helpful solutions and engagement on site. Choose from the top experts in the Hall of Fame or on the right rail of your favorite topic page. Look for the blue “Nominate” button on their profile to vote.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now