If the entity in question is a company or person you can usually understand them as being classified as an 'agent' in English. This isn't a fail-safe method, as 'proxy' (or other terms) can be used in similar circumstances in English (aka 'a healthcare proxy'), but 'agent' is a good starting point.

I'm a bit confused by your examples, as in IT I usually see this as 代理 （not 代理商）， in　which case 'proxy' is often used. However, assuming that 代理商is synonymous with 代理here, I'd start with the question of whether or not this is an server/application acting as an intermediary between two devices. If so, then 'proxy' is a good place to begin your research.

If you want to type a more specific question with a sentence/more context context that might help us in giving more specific answers.

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Note added at 19 hrs (2015-08-27 02:41:13 GMT)
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Also note that it's usually still worth checking these things. Many English services/clients with 'Agent' in their name, for example 'Network Access Protection Agent' are translated into Chinese using 代理，which can be dangerous when back translating.