# DNSServiceConstructFullName(_:_:_:_:) Concatenates a three-part domain name (as returned by the above callbacks) into a properly-escaped full domain name. ``` func DNSServiceConstructFullName(_ fullName: UnsafeMutablePointer!, _ service: UnsafePointer!, _ regtype: UnsafePointer!, _ domain: UnsafePointer!) -> DNSServiceErrorType ``` ## Parameters `fullName` A pointer to a buffer that where the resulting full domain name is to be written. The buffer must be [`kDNSServiceMaxDomainName`](/documentation/dnssd/kDNSServiceMaxDomainName) (1009) bytes in length to accommodate the longest legal domain name without buffer overrun. `service` The service name - any dots or backslashes must NOT be escaped. May be NULL (to construct a PTR record name, e.g. “_ftp._tcp.apple.com.”). `regtype` The service type followed by the protocol, separated by a dot (e.g. “_ftp._tcp”). `domain` The domain name, e.g. “apple.com.”. Literal dots or backslashes, if any, must be escaped, e.g. “1st. Floor.apple.com.” ## Return Value Returns [`kDNSServiceErr_NoError`](/documentation/dnssd/kDNSServiceErr_NoError) (0) on success, kDNSServiceErr_BadParam on error. ## Discussion Note that callbacks in the above functions ALREADY ESCAPE strings where necessary. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)