Question

I want to set up an FTP connection using a proxy server with Apache’s commons-net.

But looking at this Does FTPClient support FTP connections through an FTP proxy server? has me worried.

I have to meddle with the system properties and the Sun docs state that “If socksProxyHost is specified then all TCP sockets will use the SOCKS proxy server to establish a connection or accept one.”
WTH? All TCP sockets? What about my database connections? Or other FTP connections i might want to open at the same time not using a proxy? Will they all be affected?

Is there some other way to do it that doesn’t mess with the rest of my application?

Answer 1

You have several ways of using proxies in Java, especially from version 1.5.

1. Using System Properties: quick & powerfull but limited flexibility
   • You can use use a SOCKS proxy for all TCP connections.
   • You can also set a proxy per protocol, doable for HTTP, FTP and HTTPS
   • For both methods, you can specify a list of hosts that will not use proxy
2. Using the java.net.Proxy class (Java 1.5+) to set (or not) a Proxy per Connection
3. Impleting a java.net.ProxySelector (idem) which will determine a Proxy for each Connection according to your criteria

See the detailled Sun technote on networking & proxies.