Question

Connecting to a database server through a proxy.

Asked by: RobboRed

I normally connect to a SQL server from a C# or VB app using a connection string such as:
Data Source=<ServerIP,Port>;TRUSTED_CONNECTION=no;Persist Security Info=False;Initial Catalog=DBName;User ID=john;password=1234

This does not work when there is a proxy at the client side that blocks access through to the Internet.

All solutions I have found suggest that the client side IT staff open the proxy firewall for the required ports. In practice, people are often reluctant to open additional ports on the firewall. It is possible to go through the firewall using an HTTP tunnel, however I cannot get this to work to open a SQL connection. There are other methods available, for example Proxifier ( www.proxifier.com ) does this. Does anyone know how to do this in code, as I would prefer to avoid clients having to install an additional application on their machines.

Thanks,
Rob

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Asked On
2009-07-01 at 04:31:38ID24536056
Tags

Database

,

sql

,

proxy

,

http tunnel

,

tcp listener

Topics

Network Software Firewalls

,

Network Management

,

Transport

Participating Experts
1
Points
500
Comments
6

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Answers

 

by: giltjrPosted on 2009-07-01 at 05:05:53ID: 24753398

Unfortunately the bad part of using a proxy is not all IP based applications support using proxy.

proxifier works by "hooking" into the IP stack and intercepting the IP packets and transparently sending them to the proxy server.  Something you really can't do in code.

What I would suggest is that instead of the clients talking directly to the database server, that you write a HTTP front end to your application and have them talk to a web server and have the web server talk to the database.

 

by: RobboRedPosted on 2009-07-01 at 08:05:11ID: 24755100

Thanks for your response. A web interface is a possibility, but it is difficult to get the functionality of a Windows application so I'm still hoping there is an alternative solution.

 

by: giltjrPosted on 2009-07-01 at 10:02:54ID: 24756237

Well not really.  If you go back and read by statement, I never said you had to use a web interface.  I said you can use HTTP talking to a web server.

You still have a custom C++ (or whatever language you wish to write in) and it uses HTTP to communicate the requests back to a web server.  In fact it does not even need to be a web server, it can be a custom written server application that processes HTTP, its just a web server based application gets you out of the business of handling some of the more mundane processes of being a HTTP server.

 

by: RobboRedPosted on 2009-07-01 at 11:22:35ID: 24756846

I don't really understand where HTTP comes in. Does a connect command to a database use HTTP?

 

by: giltjrPosted on 2009-07-01 at 12:20:57ID: 24757272

No, you would  use HTTP to communicate the clients request and response to and from the server application.  The server application would then do the query against the database and then return the results to the client.

In one sense it would look like a web based application, the difference is instead of a web browser the client would be your custom program.

This way you don't have to have to have the customer install special software in order to get through their proxy server or for them to install/setup a socks server.

Otherwise they have to configure their firewall to allow direct access to your data base server without going through their proxy.

 

by: RobboRedPosted on 2009-07-02 at 02:48:49ID: 24761675

Yes, that would work, thanks.

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