How to run Bitcoin Core behind corporate proxy? I'm want to run Bitcoin Core client on TestNet and I need to config it for using under corporate proxy.
Since I'm using Squid to set proxy for my system I should set "localhost:3128" somewhere... but bitcoin-qt options seems to have only SOCK5 proxy field.

I also tried to set the proxy using the command line:

./bitcoin-qt --testnet -proxy=localhost:3298



...but it doesn't work.

How can I solve? Can I run Bitcoin Core using setting a http proxy?
Bitcoin doesn't use HTTP for its communications - it has its own specific protocol that runs directly on top of TCP.  So an HTTP proxy like squid won't help.  

If you aren't able to make outgoing TCP connections through your firewall (mainly to destination port 8333) then you'll have to contact your corporate IT people about adding appropriate firewall rules.  The same if you want to be able to enable listening.