IP Addresses, Subnets, Ports and NAT: localhost, 0.0.0.0 and Connectivity in Containers
An IP address finds an interface, a port finds a socket on that machine; a server bound to 127.0.0.1 can only be reached from inside that machine. RFC 1918 private addresses, subnets with CIDR, NAT, ephemeral ports, address already in use, and why a Kestrel bound to localhost in a container returns an Empty reply, with real output.
8 Nov 2026
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11 min
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