Does anyone have Squid3 working to successfully cache FTP requests coming in transparently? Should the proxy still listen on 3128, and I redirect incoming reuests on 21 to 3128?


Squid doesn't support FTP transparanet proxying. Squid is an HTTP proxy and only supports HTTP connection in its listening port. SO HTTP tranparent proxy only works for Squid. If you really need a transparent FTP proxy, use Frox

Squid support FTP proxying when you configure it manually in the browsers because browser request FTP object using HTTP messages in that case.

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    More specifically, Squid can passthrough FTP traffic (or any TCP traffic actually) via CONNECT requests. However it only passes through whatever data there is and can't cache nor interpret that traffic. – user186340 Jan 24 '15 at 11:10

As far as I know there is no Proxy that will support FTP transparently.

This is partly because FTP in some ways is a more complex protocol the HTTP. HTTP uses a single TCP connection for everything. FTP uses a separate TCP connection for the control channel, and for data transfers. The additional connection details for the additional TCP connections are negotiated between the client and server within the control channel.

An ftp transparent proxy would be far more complicated for FTP then HTTP.

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    Squid doesn't support transparent FTP proxying, but Frox yes. – Diego Woitasen Aug 29 '12 at 11:46

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