Long Adventure on Mono/MySQL Land!

February 19th, 2009

My head hurts. I'm porting a .NET application to Linux/Mono, and everything was working out fine, except the connectivity to the MySql database. Â I don't have experience as an administrator, so I had a machine set up, I installed mono (after so many time I still have to compile stuff on Linux? Come on!), the application worked, but I had the following issues:

I could connect to mysql on the production server using
```
mysql -u user -p
```
The application couldn't connect to mysql on the production server (using localhost)
The application could connect to mysql on another machines
The same application on another machines could connect to mysql on the production server

At this time I didn't know if the problem was with mono/application or with mysql configuration. So I run a Python script that connected to localhost and it worked fine... Then I downloaded the MySQL .NET provider sources and started to break some rocks (Portuguese expression).

The provider only said something like:

Unable to connect to any of the specified MySQL hosts.
---> System.Exception:
Exception of type 'System.Exception' was thrown.

Very usefull information as you can see. After digging up, this exception was being thrown like this:

PLAIN TEXT

C#:

StreamCreator sc = new StreamCreator(Settings.Server, Settings.Port, pipeName);
baseStream = sc.GetStream(Settings.ConnectionTimeout);
if (baseStream == null)
throw new Exception();

Really classy material. The actual exception was being thrown by:

PLAIN TEXT

C#:

Socket socket = ...
try {
socket.EndConnect(ias);
} catch (Exception) {
socket.Close();
return null;
}

Oh yeah! What more can I say?

After patching the mysql .net provider with some logging, I had the real exception:

System.Net.Sockets.SocketException: Connection refused

The I did something that I should have done a long time ago:

# telnet localhost 3306
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused

Well, it's proved that it wasn't an application / mono problem. Why did it work with direct mysql on the console and Python? Maybe because they connect using a pipe, instead of the TCP stream that the provider uses, I really don't know.

And wouldn't know how to fix this, but my colleague Paulo Pires came and saved the day. It seams that mysql was configured to use a binding to local named address, and because of that refused connections to localhost.

Posted by Pedro Santos

Filed in mono, rant, software development

6 Responses to “Long Adventure on Mono/MySQL Land!”

Alcides Says:
February 19th, 2009 at 1:42 pm
Logo ao mesmo tempo no Prt.sc estava o post da Andreia Gaita em como usar o apt-get para instalar o moonlight: http://blog.worldofcoding.com/2009/02/moonlight-shining-on-ubuntu.html

Logo o mono tb tem de dar:

sh# sudo apt-get install mono mono-gmcs mono-gac mono-utils monodevelop
Pedro Santos Says:
February 19th, 2009 at 1:49 pm
Sim, o problema Ã© se a versÃ£o que pretendes ainda nÃ£o estÃ¡ disponÃvel em pacotes, ou entÃ£o estÃ¡s numa distro que nÃ£o tem pacotes…
Carlos Rodrigues Says:
February 19th, 2009 at 4:16 pm
“I’m porting a .NET application to Linux/Mono”

But… But… I thought there was no need to port stuff between MS’ .NET and Mono…

Sorry, couldn’t resist.
Pedro Santos Says:
February 19th, 2009 at 4:19 pm
You’d be surprised Carlos.

All the major problems I’m having are related with linux configurations.
Paulo Pires Says:
February 19th, 2009 at 7:03 pm
The problem is that you’re alone migrating an environment and not just an application code to a platform which administration, apparently you’re not much aware of. As you could see it was pretty easy to solve and no code changes were needed.

Now, getting to a problem is most of the time trickier than finding its solution

Btw, do you want me to send you an Ubuntu CD for installation?