Network Problem?

lucas.delphi · Post by **lucas.delphi** » Tue 08 Nov 2011 11:46

Hi,

I'm having a problem with a customer who bought my program and would like to have information about this with you.

At first, I'm using MyDac 4.9, MySQL 5.5.6 and Delphi 2010. I just have the MyConnection and TMyQuery components in my application. The customer's business have an TCP netwotk and an external VPN network too, the server contains the database and the clients have my application running with the MySQL dlls up to date

The problem is: sometimes, when the client machine tries to connect, this returns the "host 192.168.1.2 not found". We can think thar the server can be off or the connection to the network is offline. Well, when this error occurs, I open the Windows Explorer window and call the server from there and it works, all folders are displayed.

After this, some clients can connect correctly to mysql, but some doesn't.

The customer insists in stop with the project, but I'm sure that the problem is not from my program. So I have to show a solution for the directors, or I will lose the project.

Any sugestions?

PS: Sorry for the poor english

AndreyZ · Post by **AndreyZ** » Tue 08 Nov 2011 13:05

Hello,

This problem may be caused by network settings. Please try increasing the TMyConnection.ConnectionTimeout property and check if the problem persists.

lucas.delphi · Post by **lucas.delphi** » Tue 08 Nov 2011 13:09

I've already tried this. didn't worked.

AndreyZ · Post by **AndreyZ** » Tue 08 Nov 2011 15:58

Please check that firewalls on both client and server sides do not forbid your application to connect to your MySQL server. Also you can check if connection can be establish using telnet in the following way:

Code: Select all

telnet 192.168.1.2 3306

You should run telnet from the user side.

lucas.delphi · Post by **lucas.delphi** » Tue 08 Nov 2011 16:05

I'll try the telnet command. The firewall in the server side is off and there is not any anti virus application installed (OMG).

One of the client machines had the firewall turned to OFF, but the problem sometimes occurs (as I said, it's not aways and it's not aways in the same machine). This machine uses a windows XP SP3 with NOD32 Anti Virus. The server machine uses a Windows 2008 Server.

Thanks again.

AndreyZ · Post by **AndreyZ** » Wed 09 Nov 2011 14:03

Some versions of NOD32 control network. Please check that NOD32 doesn't block your application.

lucas.delphi · Post by **lucas.delphi** » Wed 09 Nov 2011 15:42

Just checked! The AV does not block the application. As as prove, the computer sometimes connects, sometimes not.

AndreyZ · Post by **AndreyZ** » Thu 10 Nov 2011 12:42

And what are the results of telnet command I gave you? Can you connect to your server with it from a client computer?

lucas.delphi · Post by **lucas.delphi** » Thu 10 Nov 2011 12:55

I work at night, 3 times a week in this project, it's a second job, so I didn't went to work this week. Today at night I'll go and test the telnet command. Will reply when tested. Thanks again

AndreyZ · Post by **AndreyZ** » Mon 21 Nov 2011 15:25

Was the problem solved? If not, please contact us.

lucas.delphi · Post by **lucas.delphi** » Mon 21 Nov 2011 15:42

I'm really sorry for the late in the answer. Another problems envolving the project appeared.

I changed the connection timeout to 60 seconds and this resolved the problem in most of the users.

Another things I found.

The VPN users are using internet connections of 256 to 512 kbps. When using the program, they were mostly downloading files and watching sites too. Recommended use only the program in this situation. Worked fine.

The users in the internal network: we saw that the problem ocurred when too many of them were using the program at the same time. This looks like some rub or switch connection or bad configuration. Still waiting for the positition of the customer.

With this, I think that we have 50% of the problem resolved and proved firmly that the problem does not comes from my program, neighter the MyDAC library.

With this facts, I can take this topic as closed and resolved. Thanks everybody for the help. Nedding some thing in delphi programming and SQL knowlege, you can contact-me at any time.

Regards.

AndreyZ · Post by **AndreyZ** » Mon 21 Nov 2011 15:58

It's good to see that the problem was solved. Feel free to contact us if you have any other questions about MyDAC.