Connection reset by peer

Jason Orendorff jason at
Fri Dec 14 11:52:15 EST 2001

Edward wrote:
> udpCliSock=socket(AF_INET,SOCK_DGRAM)
> data=raw_input('>')
> udpCliSock.sendto(data,ADDR)
> print udpCliSock.getsockname()
> data, addr = udpCliSock.recvfrom(BUFSIZ)

Hmm.  It is definitely weird to get ECONNRESET back from a
non-connection-oriented socket.

Well, here's my guess at what's happening.
 * Client sends a UDP packet; this gets sent to the server
   over the network.
 * Server IP layer receives the packet.
 * Server IP layer provides a copy of the packet to the server,
   since the server is listening on a raw socket.
 * Server IP layer then notices that there is no UDP socket
   there, on the server, bound to the specified port.
 * Server IP layer therefore generates an ICMP "Port Unreachable"
   error packet and sends it back to the client.
 * Client IP layer receives the error packet and sets a flag on
   the udpCliSock saying "hey, you got an error"
 * The next time you call udpCliSock.recvfrom(), the error gets

This is just a guess though.

If the guess is correct, then you can make this work by
creating a udpServerSock on the server; you can set it to
nonblocking, occasionally do udpServerSock.recvfrom() on it,
and discard the results.

Good luck.

Jason Orendorff

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