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Is it possible to receive any empty payload with recvfrom() with SOCK_DGRAM based socket? The server is only interested in the client header to send it back a message (i.e. single message, send only protocol).

user7434748
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  • Yes. You can send zero-length datagrams with UDP. – user207421 Feb 17 '17 at 11:23
  • @EJP How? `recvfrom()` never blocks on zero-lengths, and attempting to send empty package using for example `cat /dev/null | nc -u 127.0.0.1 1234` with `recvfrom()` in busy waiting does nothing. – user7434748 Feb 17 '17 at 22:04
  • With `send()`, or `sendto()`, supplying a zero length parameter. `recvfrom()` will block until a datagram is received or an error occurs. – user207421 Feb 18 '17 at 21:10
  • @EJP `recvfrom()` in my case never blocks and always returns zero. – user7434748 Feb 20 '17 at 09:39

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0-sized datagrams are perfectly valid from socket API perspective and at least protocols IP, UDP, UNIX: one can send and receive them.

Maxim Egorushkin
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