The PortQry.exe utility is a convenient tool to check the response of TCP/UDP ports on hosts to diagnose issues related to the operation of various network services and firewalls in TCP/IP networks.

<p>As with any network and internet-capable computing system, many of Apple's services and programs require access to the internet and/or local network using TCP and UDP ports to function properly ...

27 under udp is part of smtp, rather esmtp - pop mail service of SLMail. If it is port 27, it is TCP NSW (National Software Works).<BR><BR>Port 20670 I thought was one of the old gaming ports but ...

According to this group, starting with February 1, 2020, DNS servers that can't handle DNS queries over both UDP and TCP may be pushed out of the DNS ecosystem and stop working.