Comment 4 for bug 1742876

Test 1:
With /etc/systemd/system/epmd.socket as
-----------------------------------
[Unit]
Description=Erlang Port Mapper Daemon Activation Socket

[Socket]
ListenStream=127.0.0.1:4369
#ListenStream=10.101.0.11:4369
Accept=false

[Install]
WantedBy=sockets.target
-------------------------------------

controller:~ # service rabbitmq-server status
● rabbitmq-server.service - RabbitMQ broker
   Loaded: loaded (/usr/lib/systemd/system/rabbitmq-server.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Mon 2018-01-15 09:42:46 +0530; 48s ago
  Process: 1794 ExecStop=/usr/sbin/rabbitmqctl stop (code=exited, status=0/SUCCESS)
  Process: 1478 ExecStart=/usr/sbin/rabbitmq-server (code=exited, status=1/FAILURE)
 Main PID: 1478 (code=exited, status=1/FAILURE)

Jan 15 09:42:46 controller rabbitmqctl[1794]: attempted to contact: [rabbit@controller]
Jan 15 09:42:46 controller rabbitmqctl[1794]: rabbit@controller:
Jan 15 09:42:46 controller rabbitmqctl[1794]: * unable to connect to epmd (port 4369) on controller: address (cannot connect to host/port)
Jan 15 09:42:46 controller rabbitmqctl[1794]: current node details:
Jan 15 09:42:46 controller rabbitmqctl[1794]: - node name: 'rabbitmq-cli-79@controller'
Jan 15 09:42:46 controller rabbitmqctl[1794]: - home dir: /var/lib/rabbitmq
Jan 15 09:42:46 controller rabbitmqctl[1794]: - cookie hash: R6aclPnr+k4dau9mL3XKrg==
Jan 15 09:42:46 controller systemd[1]: Failed to start RabbitMQ broker.
Jan 15 09:42:46 controller systemd[1]: rabbitmq-server.service: Unit entered failed state.
Jan 15 09:42:46 controller systemd[1]: rabbitmq-server.service: Failed with result 'exit-code'.

Test 2:

With /etc/systemd/system/epmd.socket as
-----------------------------------
[Unit]
Description=Erlang Port Mapper Daemon Activation Socket

[Socket]
#ListenStream=127.0.0.1:4369
ListenStream=10.101.0.11:4369
Accept=false

[Install]
WantedBy=sockets.target
-----------------------------------

controller:~ # service rabbitmq-server status
● rabbitmq-server.service - RabbitMQ broker
   Loaded: loaded (/usr/lib/systemd/system/rabbitmq-server.service; enabled; vendor preset: disabled)
   Active: inactive (dead)

Jan 15 09:46:22 controller systemd[1]: Dependency failed for RabbitMQ broker.
Jan 15 09:46:22 controller systemd[1]: rabbitmq-server.service: Job rabbitmq-server.service/start failed with result 'dependency'.

controller:~ # service rabbitmq-server start
Job for rabbitmq-server.service failed because the control process exited with error code. See "systemctl status rabbitmq-server.service" and "journalctl -xe" for details.

Test 3:
With /etc/systemd/system/epmd.socket as
-------------------------------------
[Unit]
Description=Erlang Port Mapper Daemon Activation Socket

[Socket]
ListenStream=127.0.0.1:4369
ListenStream=10.101.0.11:4369
Accept=false

[Install]
WantedBy=sockets.target
-------------------------------------
controller:~ # service rabbitmq-server status
● rabbitmq-server.service - RabbitMQ broker
   Loaded: loaded (/usr/lib/systemd/system/rabbitmq-server.service; enabled; vendor preset: disabled)
   Active: inactive (dead)

Jan 15 09:57:38 controller systemd[1]: Dependency failed for RabbitMQ broker.
Jan 15 09:57:38 controller systemd[1]: rabbitmq-server.service: Job rabbitmq-server.service/start failed with result 'dependency'.

controller:~ # service rabbitmq-server start
controller:~ # service rabbitmq-server status
● rabbitmq-server.service - RabbitMQ broker
   Loaded: loaded (/usr/lib/systemd/system/rabbitmq-server.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2018-01-15 09:58:43 +0530; 2s ago
 Main PID: 1849 (beam.smp)
   Status: "Initialized"
    Tasks: 76 (limit: 512)
   CGroup: /system.slice/rabbitmq-server.service
           ├─1843 /bin/sh /usr/sbin/rabbitmq-server
           ├─1849 /usr/lib64/erlang/erts-8.3.2/bin/beam.smp -W w -A 64 -P 1048576 -t 5000000 -stbt db -zdbbl 128000 -K true -- -root /usr/lib64/erlang -progname erl -- -home /var/lib/rabbitmq -- -pa /usr/lib64/rabbitmq/lib/rabbitmq_server-3.6.11/ebin -noshell -noinput -s rabbit boot -sname rabbit@controller -boot start_sasl -config /etc/rabbitmq/rabbitmq -kernel inet_default_connect_options [{nodelay,true}] -sasl errlog_type error -sasl sasl_error_logger false -rabbit error_logger {file,"/<email address hidden>"} -rabbit sasl_error_logger {file,"/<email address hidden>"} -rabbit enabled_plugins_file "/etc/rabbitmq/enabled_plugins" -rabbit plugins_dir "/usr/lib64/rabbitmq/lib/rabbitmq_server-3.6.11/plugins" -rabbit plugins_expand_dir "/var/lib/rabbitmq/mnesia/rabbit@controller-plugins-expand" -os_mon start_cpu_sup false -os_mon start_disksup false -os_mon start_memsup false -mnesia dir "/var/lib/rabbitmq/mnesia/rabbit@controller" -kernel inet_dist_listen_min 25672 -kernel inet_dist_listen_max 25672
           ├─2058 erl_child_setup 65535
           ├─2072 inet_gethost 4
           └─2073 inet_gethost 4

This behavior is strange as rabbitmq-server.service is enabled through 'systemctl start rabbitmq-server.service'
The /var/log/messages says,

Jan 15 09:58:39 controller systemd[1]: Starting RabbitMQ broker...
Jan 15 09:58:43 controller systemd[1]: rabbitmq-server.service: Supervising process 1849 which is not our child. We'll most likely not notice when it exits.
Jan 15 09:58:43 controller systemd[1]: Started RabbitMQ broker.

2018-01-15T10:01:32.517197+05:30 controller systemd[1]: epmd.socket: Failed to listen on sockets: Cannot assign requested address
2018-01-15T10:01:32.517209+05:30 controller systemd[1]: Failed to listen on Erlang Port Mapper Daemon Activation Socket.
2018-01-15T10:01:32.517225+05:30 controller systemd[1]: Dependency failed for Erlang Port Mapper Daemon.
2018-01-15T10:01:32.517236+05:30 controller systemd[1]: Dependency failed for RabbitMQ broker.
2018-01-15T10:01:32.517247+05:30 controller systemd[1]: rabbitmq-server.service: Job rabbitmq-server.service/start failed with result 'dependency'.
2018-01-15T10:01:32.517258+05:30 controller systemd[1]: epmd.service: Job epmd.service/start failed with result 'dependency'.
2018-01-15T10:01:32.517269+05:30 controller systemd[1]: epmd.socket: Unit entered failed state.