Question

Hi’ I’m writing a simple http port forwarder. I read data from port 80, and pass the data to my lighttpd server, on port 8080.

As long as I write() data on the socket on port 8080 (forwarding the request) there’s no problem, but when I read() data from that socket (forwarding the response), the last read() hangs a lot (about 1 or 2 seconds) before realizing there’s no more data and returning 0.

I tried to set the socket to non-blocking, but this doesn’t work, as sometimes it returns EWOULDBLOCKING even if there’s some data left (lighttpd + cgi can be quite slow).
I tried to set a timeout with select(), but, as above, a slow cgi could timeout the socket when there’s actually some data to transmit.

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Update: SOLVED. It was the keepalive after all. After I disabled it in my lighttpd configuration file, the whole thing runs flawlessly.

Answer 1

Well, for the sake of completion, and as per my comment:

It is likely that the HTTP server itself (lighttpd in your case) is maintaining a persistent connection to your proxy because your proxy relayed a header containing “Connection: keep-alive”. This header aids when the client wants to make multiple requests over the same connection. So, because lighttpd received this header, it assumed it was going to receive further requests and kept the socket open, causing read to block in your proxy.

Disabling keep-alive in your lighttpd configuration is one way to fix it, but also you could also strip the “Connection: keep-alive“ from the header before you relay it to your web server.