Problems Connecting to peers (Error 503 Service Unavailable)

I am recently having problems connecting to peers through our company proxy. It was working yesterday and everything suddenly stopped. I can connect to the trackers without problems but when it starts connecting to peers nothing happens

I monitored the connections/packets made to/from our proxy (only utorrent was running) using wireshark. My computer is sending connect requests to peers but the proxy returns the Error 503 service unavailable error.

What could be the cause of this? Could the ISP be blocking the connections or the peers?

I haven't changed anything and the dloads were going fine until suddenly everything stopped. I even tried connecting to the tracker using anonymous proxies and then change back to my proxy once the connection to the tracker was successful and it got the peer list.

Using the latest utorrent

Could it be that the squid proxy disabled http connect, or only allowing certain ports for http connect? I understand utorrent needs http connect to connect to peers through proxy so is there anyway around it like using http-get or some other http protocol to connect to peers?

This is what i captured in wireshark when utorrent is connecting to peers (not exact format)

local: my LAN IP

remote: company proxy

Http Connect (Peer IP:Peer PORT)

the next is

503 unavailable

regarding the connection to the peer

HTTP Connect is probably blocked or disabled now, a quick poke seems to indicate it only takes one line in Squids configuration. Do you need to have the proxy details entered for that particular setup? You'll probably have to torrent at home or somehow get approval.

I guess they just disabled other ports for HTTP CONNECT except for SSL(443) and other http ports 8080, 80 etc. Tested it by monitoring ultrasurf. The only solution is to ask the peers to change their ports to 443 to be able to connect to them which is not likely to happen.

192 102.500755 <my ip> <proxy> HTTP CONNECT <ip of anon proxy>:443 HTTP/1.0 Continuation or non-HTTP traffic

194 102.505496 <my ip> <proxy> HTTP HTTP/1.0 200 Connection established

HTTP Connect is probably blocked or disabled now, a quick poke seems to indicate it only takes one line in Squids configuration. Do you need to have the proxy details entered for that particular setup? You'll probably have to torrent at home or somehow get approval.