c# - Check if a remote port is UP(listening) on UDP? -

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i've detect if remote host up, based on it's service(ip+port) running. can't use ping because need make works icmp port blocked.

sometime service using tcp, udp(but when i've check, know if server has run on udp or tcp, it's depending of it's type). i've no issue checking tcp port(based on https://stackoverflow.com/a/7605428/397830 ). since udp not connection oriented protocol, how sure remote host listening on udp on port?

thank you!

excerpt nmap documentation:

udp scan works sending udp packet every targeted port. common ports such 53 , 161, protocol-specific payload sent, ports packet empty. --data-length option can used send fixed-length random payload every port or (if specify value of 0) disable payloads. if icmp port unreachable error (type 3, code 3) returned, port closed. other icmp unreachable errors (type 3, codes 1, 2, 9, 10, or 13) mark port filtered. occasionally, service respond udp packet, proving open. if no response received after retransmissions, port classified open|filtered. means port open, or perhaps packet filters blocking communication. version detection (-sv) can used differentiate open ports filtered ones.

you can read full article here: nmap port scanning


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