What does this client do?
Difficult to know, but just for curiosity I'd set up a PHP script at that url to play with your pal:
- get the client IP address and scan it immediately (open ports, reverse address, whois information on the netblock)
- dump HTTP headers to look into them. If it sends a referrer maybe it's coming from somewhere else. Look for other interesting things.
- reply with an HTTP redirect to some URL you manage and see if it follows it. Just to know...
- if you have lots of bandwidth try replying with some gigabytes of garbage :)
- (and while you're at it, measure how fast he can digest data)
- when you're bored of playing with him then go tarpitting him (if you have enough resources): everytime it connects enter some long sleep() before completing the HTTP reply. Make him consume more resources.
why is it calling this page continuously?
Did you try to ask Google? Seems like Tencent Traveler is one of the most popular browser in China. Maybe someone with it visited your site, or tried to visit invalid URLs on your site, maybe there's a spider run by the software house trying to index / scan / cache the sites visited by its browser users. Or maybe it's just a chinese bored boy, or maybe an infected PC, or... who knows, you should also ask him directly, but you need to know who he is.
And how can I prevent this?
To actually prevent him for trying, you should report it as a spammer to someone/something that has authority over him. Usually this is the Technical Contact (or tech-c, or abuse, or whatever they call it) of the AS responsible for its IP range. You can find that piece of information from whois.
If prevention does not succeed and it keeps doing those requests, you can block them in various ways:
if they come from a single subnet and you're not interested in that public, block the whole subnet at the IP level (eg. if it comes from a Chinese /8 subnet and you don't mind blocking chinese clients, simply drop traffic from the whole subnet)
block all requests matching that User-Agent at the HTTP level if you have no known legitimate users with the very same User-Agent.
Why do these aggressive bots always come from China or Russia?
Ahhh, life would be easier if that was actually true ;)
it distorts the visitors statistic significantly
You're talking about one hit per 5 minutes, or roughly 0.003hit/second - should be well below the noise floor.. Please rephrase your question and explain what you mean by "distorts".