mdnsd - embeddable Multicast DNS Daemon

About
Usage
- Service Records
Build & Install
Origin & References

About

Jeremie Miller's original mDNS/mDNS-SD library daemon.

Download a relased tarball (not a GitHub zip) to unlock a fully supported version. Hardcore devs. can proceed to clone the GIT repository, see below for help.

Usage

mdnsd by default reads service definitions from /etc/mdns.d/*, but a different path can be given, which may be a directory or a single file.

Usage: mdnsd [-hnpsv] [-a ADDRESS] [-l LEVEL] [PATH]

    -a ADDR   Address of service/host to announce, default: auto
    -h        This help text
    -i IFACE  Interface to announce services on, and get address from
    -l LEVEL  Set log level: none, err, notice (default), info, debug
    -n        Run in foreground, do not detach from controlling terminal
    -p        Persistent mode, retry if the socket or interface is lost
    -s        Use syslog even if running in foreground
    -t TTL    Set TTL of mDNS packets, default: 1 (link-local only)
    -v        Show program version

Bug report address: https://github.com/troglobit/mdnsd/issues

By default mdnsd daemonizes, detaches from the controlling terminal and continues running in the background, logging errors (or debug messages if enabled) to the systmem log. There is no output to be expected. On GNU/Linux, use mdns-scan or Wireshark to verify your setup. Other operating systems have their own set of tools for mDNS-SD and mdnsd may not even have a place there.

mdnsd currently only runs on one system interface. To figure out which to use, the system routing table is queried, specifically the default route. To run on systems without a default route, e.g. a link-local only system, use -i IFACE. Starting mdnsd early in the boot process means the system may not yet have acquired an IP address, or the interface itself may not even exist yet, in which case -p may likely also help.

See the file API.md for pointers on how to use the mDNS library.

Service Records

This section provides a couple of service record examples. The syntax of the files is fairly free form. Optional directives: name, txt, target, and cname.

Note: you need at least one service record for mdnsd to respond to queries from, e.g., mdns-scan.

FTP service example:

# /etc/mdns.d/ftp.service -- mDNS-SD advertisement of FTP service
name Troglobit FTP Server
type _ftp._tcp
port 21
txt server=uftpd
txt version=2.6
target ftp.luthien.local
cname ftp.local

HTTP service example:

# /etc/mdns.d/http.service -- mDNS-SD advertisement of HTTP service
name Troglobit HTTP Server
type _http._tcp
port 80
txt server=merecat
txt version=2.31
target www.luthien.local
cname home.local

SSH service example:

# /etc/mdns.d/http.service -- mDNS-SD advertisement of SSH service
name Dropbear SSH Server
type _ssh._tcp
port 22

Build & Install

This project is built for and developed on GNU/Linux systems, but should work on any UNIX like system. Use the standard GNU configure script to create a Makefile for your system and then call make.

./configure
make all
make install

Users who checked out the source from GitHub must run ./autogen.sh first to create the configure script. This requires GNU autotools and pkg-config to be installed on the build system.

If you install to the default location used by the configure script, the library is installed in /usr/local/lib, which may not be in the default search path for your system. Depending on the C library used, the file /etc/ld.so.conf may exist (there may also be a sub-directory). If /usr/local/lib is already listed there, you may need to update the cache:

ldconfig -v |grep mdnsd

If you don't get any output from the above command, the ld.so.conf needs updating, or you may not be using the GNU C library.

Origin & References

This mDNS-SD implementation was developed by Jeremie Miller in 2003, originally announced on the rendezvous-dev mailing list. It has many forks and has been used by many other applications over the years.