Description of problem: A week ago, this new package landed in Fedora, introducing alternatives to the /bin/nc. The new netcat provides the following /usr/bin/nc /usr/bin/netcat While the old one: /usr/bin/nc /usr/bin/ncat The nc binary symlins either of these based on the non-copletely transparent update-alternatives. While the ncat alternative properly detected the EOF and closes connection: (first terminal) # ncat -l 8080 XXX # (second terminal) # echo XXX | ncat localhost 8080 # the new netcat does not and keeps hanging both client and server after reading the EOF: (first terminal) # netcat -l 8080 XXX (second terminal) # echo XXX | netcat localhost 8080 Version-Release number of selected component (if applicable): netcat-1.217-3.fc34.x86_64 nmap-ncat-7.80-11.fc34.x86_64 How reproducible: always Steps to Reproduce: 1. Send EOF to netcat Actual results: EOF is not propagated to the other side of socket Expected results: the EOF is sent to listener, socket is closed, command terminates. Additional info: This is a regression if the netcat gets installed instead of nmap-ncat.
This particular use case is even described in the manual page of netcat: > The connection may be terminated using an EOF (‘^D’). (assuming the echo/bash sends the EOF correctly to the netcat)
I am not sure whether I can address this, because like /usr/sbin/sendmail is not a 100% alternative when using Postfix, Exim etc. rather Sendmail itself, it's similar for /usr/bin/nc. Same situation also applies e.g. for /usr/bin/ksh regarding ksh93 or mksh. In case a software relies on a specific behaviour it IMHO should use the specific implementation directly (e.g. ncat) rather via the alternatives symlink (nc). Your report however brings me to the question whether you installed netcat yourself explicitly or whether it happened by accident (sloppy package dependency or packaging mistake etc.). The intention was to provide the original OpenBSD netcat additionally for those who want it, not to break everybody's scripts, behaviour etc. by default (like the hard and mostly by Red-Hat-driven switch from the original "nc" RPM package to "nmap-ncat" like 5+ years ago did).
Indeed, I am not striving for 100% compatibility, but I would like to have the a use case which is described in the manual page of the new netcat package working (as mentioned in the comment #1). The dependency in a test I had was written just as a "nc" and in one system, where the nmap-ncat was installed, the above worked just fine, but in other system where nothing was installed, the netcat got a preference for some reason, which might cause some problems for some users. Not sure how the alternatives preferences and such work in detail though.
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