MSDTC

We had some really strange problems getting MSDTC to work recently, specifically upgrading to VS2010 and SL4. Our developer environments are pointing to networked database servers and during this particular use-case the development workstation is running a both the hosted Silverlight Client and the Business Logic (API) served through a WCF service (both in Cassini). The API is performing the transactional logic.

So, working through the bugs and error messages that we got;

The first error requires MSDTC to be started (which is wasn’t by default):

The transaction manager has disabled its support for remote/network transactions. Both the WCF Server (in our case the developer workstation) and the Database Server have to have MSDTC running. Start MSDTC using the command line: NET START MSDTC

YMMV, but on Win7 the default properties for DTC also had to be updated. From Component Services MMC, navigate to Computers | My Computer | Distributed Transaction Coordinator | Local DTC. Right click + Properties and set as follows:

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Next error then relates to the default firewall setting:

The MSDTC transaction manager was unable to pull the transaction from the source transaction manager due to communication problems. Possible causes are: a firewall is present and it doesn’t have an exception for the MSDTC process, the two machines cannot find each other by their NetBIOS names, or the support for network transactions is not enabled for one of the two transaction managers. Sometimes we didn’t get this exception, and got a timeout instead and the failed transaction could be seen in the outstanding transactions list.

To resolve this we updated the Windows Firewall to add an inbound and outbound tunnel for %SystemRoot%\System32\msdtc.exe

All seems to OK … for now… :S

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