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The set of applications I work on all access the same 8 or so web services that we have. These services and applications all reside on the same box and all use the computer name when trying to connect to the web service.

For Example:

If I have a web service called MapDataService and I have an application that accesses it, it would access it by the URL: http://COMPUTERNAME/MapDataService/MapDataService.asmx.

This works in most of the applications that access the web service. However, we have several applications that, when using the computer name in the URL, will not get data returned from the service (actually a 503 is returned). In order to get it to work, the IP address of the system needs to be used in place of the COMPUTERNAME.

This strikes me as very odd considering, as I mentioned before, all applications and services are on the same box and most other applications usr the COMPUTERNAME with no issues.

Can someone give me some insight as to what could be causing this? We have no access to IIS logs and what logs we did get (this is on a customer site) are not very useful.

AWinters
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3 Answers3

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I agree with BillN.

AWinters, 503 errors are supposed to only be sent by the server to the client when, "the server is currently unable to handle the request due to a temporary overloading or maintenance of the server." (http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html) It could be that your client is reporting this incorrectly, whenever the server doesn't respond (in a certain amount of time).

Try PING COMPUTERNAME from those clients that can't connect to the web service. Assuming the server responds to Pings in general, that will tell you whether DNS is working correctly.

You can manually enter the server's COMPUTERNAME into the client's HOSTS file to see if that helps but if it does, there is some other DNS issue and editing HOSTS is just a band-aid. Fix the real issue, if possible.

It's also possible, based on the limited info we have, that the server really is temporarily overloaded sometimes. If you always get 503's when the COMPUTERNAME is used and never get it when the IP address is used, that's probably not the case though.

Mark Henderson
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Are the Apps all being run on the same system? It sounds like some of the apps are not resolving host name to the IP address, so you have to do it for them. I'd look at DNS/host file issues.

BillN
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  • They are all installed on the same system. There are about 12 apps. They are all using the server name to connect and only three are having issues. – AWinters Jan 15 '10 at 17:18
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You say there are several apps that can't get to the webservice with computername. Can other apps get to that webservice with computername ok? Can you manually with a browser?

If some apps work against one webservice, and others don't against the SAME webservice, I'd suggest it's a problem with the internal settings in the client apps (connection string, etc.)

If it's all apps against a specific webservice, then I'd take a look and see if you're using host headers or something that might be blocking specific DNS names. Or that the app's config is using the correct authentication, etc..

Phillip Jubb
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