Host name syntax

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Note: This special syntax is generally not used from the user interfaces of wc3270 or wx3270, except in scripts or at the x3270> prompt. Those user interfaces allow these options to be specified separately, and construct a properly-formatted host name from them.

Basic syntax

The basic syntax is:

[prefix:...] host [:port] [=accept-name]


An optional prefix is a single letter and a colon character (:). Multiple prefixes can be specified. Prefixes are listed here.


The host is either a fully-qualified domain name (e.g., or a numeric address in either IPv4 dotted-decimal or IPv6 hexadecimal format. A numeric IPv6 addres must be surrounded by square-bracket characters, e.g., [100:200::1], to keep the colon characters from being misinterpreted.


The optional port is a number separated from the host name by a colon. It overrides the default value of 23 (the TELNET port).

Accept name

The optional accept name is separated from the host and optional port by an equals sign (=). It overrides the value of the acceptHostname resource, specifying a name to match against the host's TLS certificate.


Connect to without a TLS tunnel, on port 23.

Connect to with a TLS tunnel but not verifying the host certificate, on port 9100.

Connect to IPv4 address on port 23.

Connect to IPv6 address 100:200::1 on port 23.


Connect to IPv6 address 100:200::1 on port 9100 with a TLS tunnel, using myhost to match the name from the host's TLS certificate.