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I have a squid proxy running in a docker container, started like this:
docker run --privileged -d --publish=3128:3128 --name foo squid
I want to get some information from it, from another container called bar.
docker run --rm -it --name bar ubuntu:trusty bash
If I run this in the bar container:
nc 172.17.0.1 3128
HEAD /
Then I get some output from the server. But if I run this:
echo 'HEAD /' | nc 172.17.0.1 3128
I get nothing. Why not?
Probably because netcat exits shortly after getting an end-of-file on its standard input. Try
(echo 'HEAD /'; sleep 5) | nc 172.17.0.1 3128
to keep netcat's local input open long enough
for it to read the network data and write it to the standard output.
The 5 is the number of seconds to delay.
Netcat has an option to deal with this. If you specify a negative quit timeout, it will wait for the network connection to close instead of quitting after EOF on stdin:
echo 'HEAD /' | nc -q -1 172.17.0.1 3128
sleep 5. Is there a difference in the buffer sizes, or something?
-q -1 will tell it not to quit after receiving EOF; it waits instead for the connection to close.