Why ZeroMQ C# PUB/SUB throws an EINVAL warning on pgm-protocol?

Question

I am completely new to ZeroMQ, my Window C# application is going to publish data through ( tcp://localhost:5563 ), if I change it to ( pgm://localhost;233.255.0.1:5555 ), throws an error:

EINVAL(22): Invalid argument

Warn: Interface {xxx-xxx-xxx..-xxx} reports as a loopback device.

Anyone can give some hints?

Answer 1

^{A use of epgm://<IPv4_ADDR>;<mcast_ADDR>:<port#> is advised in ZeroMQ API documentation.}

ZeroMQ API documentation remarks are all important:

Connecting a socket

When connecting a socket to a peer address using zmq_connect() with the pgm or epgm transport, the endpoint shall be interpreted as an interface followed by a semicolon, followed by a multicast address, followed by a colon and a port number.

An interface may be specified by either of the following:

- The interface name as defined by the operating system.
- The primary IPv4 address assigned to the interface, in its numeric representation.

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Interface names are not standardised in any way and should be assumed to be arbitrary and platform dependent. On Win32 platforms no short interface names exist, thus only the primary IPv4 address may be used to specify an interface. The interface part can be omitted, in that case the default one will be selected.

A multicast address is specified by an IPv4 multicast address in its numeric representation.