@verb{#|some command#} format. @code{/bin/sh -c "some command"} will
start and its @code{stdin}/@code{stdout} used as a connection.
+ To use @ref{Yggdrasil} network for connectivity, use
+ @verb{|yggdrasil:PUB;PRV;PEER[,...]|} format, read about
+ @ref{CfgYggdrasilAliases, possible aliases} usage.
+
May be omitted if either no direct connection exists, or
@ref{nncp-call} is used with forced address specifying.