UrlConnection连接和Socket连接是有区别的

参考

http://zhoujianghai.iteye.com/blog/1195988
http://www.coderanch.com/t/350517/Servlets/java/socket-http-connection

in ODC, there is a proxy server. It can tell us UrlConnection is different from Socket.

This proxy server, only open http, but block socket5

So you set System.setProperty("java.net.useSystemProxies", "true");, then use UrlConnection. It OK

But httpclient failed. It use socket. Exception in thread "main" java.net.SocketException: Malformed reply from SOCKS server

For connections where you specify the a protocol, such as HTTP, use URL. This handles the Socket stuff for you because it has to provide the protocol. For connections where you want to work directly with a socket, you have to specify host and port, etc. but you have to provide your own protocol handling.