# Nonterminals in server descriptors ```text nickname ::= between 1 and 19 alphanumeric characters ([A-Za-z0-9]), case-insensitive. hexdigest ::= a '$', followed by 40 hexadecimal characters ([A-Fa-f0-9]). [Represents a relay by the digest of its identity key.] ``` exitpattern ::= addrspec ":" portspec portspec ::= "\*" | port | port "-" port port ::= an integer between 1 and 65535, inclusive. ```text [Some implementations incorrectly generate ports with value 0. Implementations SHOULD accept this, and SHOULD NOT generate it. Connections to port 0 are never permitted.] ``` addrspec ::= "\*" | ip4spec | ip6spec ipv4spec ::= ip4 | ip4 "/" num_ip4_bits | ip4 "/" ip4mask ip4 ::= an IPv4 address in dotted-quad format ip4mask ::= an IPv4 mask in dotted-quad format num_ip4_bits ::= an integer between 0 and 32 ip6spec ::= ip6 | ip6 "/" num_ip6_bits ip6 ::= an IPv6 address, surrounded by square brackets. num_ip6_bits ::= an integer between 0 and 128 bool ::= "0" | "1"