SRV Record Builder

Builds an SRV presentation record. Clients first use the lowest reachable priority; within one priority, weight gives relative selection probability, so this tool does not simulate a live selection. All three numeric fields are unsigned 16-bit values. A target of `.` means the service is unavailable; using zero priority, weight, and port keeps such a record easy to read (RFC 2782). Service and Protocol are validated by different rules. Service follows the RFC 6335 §5.1 service-name syntax, which §5.2 makes mandatory for the SRV Service label: 1–15 letters, digits or hyphens with at least one letter, no leading, trailing or adjacent hyphens. Protocol follows RFC 2782 as updated by RFC 8553 §3.1: the symbolic protocol name with `_` prepended, case-insensitive, and its registration in the IANA Underscored and Globally Scoped DNS Node Names registry is a SHOULD — the RFCs put no further syntax rule on it. As a QuickKit input policy the protocol is limited to a 1–62-character LDH label (letters, digits, hyphens not at either end) so that `_` + label fits a DNS label; that limit is not an RFC requirement. For both fields a leading `_` is optional, the record is emitted in lower case, and an unregistered name is accepted because registration is recommended, not required, in both registries. `_tcp` and `_udp` are the values RFC 2782 calls most useful; `_tcp`, `_udp`, `_sctp` and `_dccp` are the registry's SRV entries that cite RFC 2782, and the registry also holds other SRV global underscored names such as `_sip` and `_xmpp`. Names are treated as absolute. Domain is the Name suffix of the `_Service._Proto.Name` owner (RFC 2782), written in RFC 1035 §5.1 presentation syntax: any label octet is legal, so `-`, `_`, `\.`, `\032` and other `\DDD` escapes are accepted and re-encoded canonically. An asterisk label such as `*.example.com` is accepted as the suffix too: the built owner `_sip._tcp.*.example.com.` is not a wildcard domain name, because RFC 4592 judges that by the leftmost label, which is `_sip` (RFC 4592 §4.5 uses exactly this SRV case) — unlike a CAA owner `*.example.com`, where the asterisk label is leftmost and the owner is a wildcard. The complete owner, `_service._proto` labels included, must fit 255 octets. The target must be a host name without escapes, and a single label needs a trailing dot. `xn--` labels are passed through without IDNA validation. TTL is 0–2147483647 (RFC 2181).