OHS instance failed to start because of (98)Address already in use: AH00072: make_sock: could not bind to address XXX.XXX.XXX.XX:7777

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Environment Details:
OHS: 12.2.1.3.0

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Problem Summary:
When we are trying to start OHS instance it's failing with an error (98)Address already in use: AH00072: make_sock: could not bind to address XXX.XXX.XXX.XX:7777

Have verified port 7777 if it's already used using lsof and netstat but nothing was listening on that port. It was free.
@machine1 config]# /usr/sbin/lsof -i:7777
@machine1 config]# netstat | grep 7777
@machine1 config]# netstat

Error:
Starting server ohs1 ...
Nov 05, 2017 12:56:48 PM oracle.ohs.plugin.nodemanager.OhsProcessManagementPlugin$ProcessImpl start
INFO: Starting server ohs1
Nov 05, 2017 12:56:48 PM oracle.ohs.plugin.nodemanager.OhsRunCommand execute
INFO: Running /u02/oracle/middleware/oracle_home/wlserver/../ohs/bin/launch httpd -DOHS_MPM_EVENT -d /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1 -k start -f /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1/httpd.conf
Nov 05, 2017 12:56:49 PM oracle.ohs.plugin.nodemanager.OhsRunCommand runGeneric
INFO: (98)Address already in use: AH00072: make_sock: could not bind to address XXX.XXX.XXX.XX:7777
Nov 05, 2017 12:56:49 PM oracle.ohs.plugin.nodemanager.OhsRunCommand runGeneric
INFO: no listening sockets available, shutting down
Nov 05, 2017 12:56:49 PM oracle.ohs.plugin.nodemanager.OhsRunCommand runGeneric
INFO: AH00015: Unable to open logs
Nov 05, 2017 12:56:49 PM oracle.ohs.plugin.nodemanager.OhsRunCommand execute
SEVERE: /u02/oracle/middleware/oracle_home/wlserver/../ohs/bin/launch httpd -DOHS_MPM_EVENT -d /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1 -k start -f /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1/httpd.conf: exit status = 1
Nov 05, 2017 12:56:49 PM oracle.ohs.plugin.nodemanager.OhsProcessHandler buildProcess
INFO: Check the instance log file for more information: /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/servers/ohs1/logs/ohs1.log
Nov 05, 2017 12:56:49 PM oracle.ohs.plugin.nodemanager.OhsProcessManagementPlugin$ProcessImpl buildIoException
SEVERE: Failed to start the server ohs1
<Nov 5, 2017 12:56:49 PM IST> <WARNING> <Server start command for OHS server 'ohs1' failed due to: [Failed to start the server ohs1
Check log file /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/system_components/OHS/ohs_nm.log
Check log file /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/servers/ohs1/logs/ohs1.log]. Please check Node Manager log and/or server 'ohs1' log for detailed information.>

This Exception occurred at Sun Nov 05 12:52:39 IST 2017.
weblogic.nodemanager.NMException: Received error message from Node Manager Server: [Server start command for OHS server 'ohs1' failed due to: [Failed to start the server ohs1


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Root Cause:
There were 2 things which were creating above problem,
1. System wasn't connected to network. Network was OFF.
2. /etc/hosts was having wrong ip configured.

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Resolution:
1. Have connected system to network. Network ON.
2. Have edited /etc/hosts and configured the correct IP.
3. Restarted OHS and it came up fine.
Starting server ohs1 ...
Nov 05, 2017 1:11:07 PM oracle.ohs.plugin.nodemanager.OhsProcessManagementPlugin$ProcessImpl start
INFO: Starting server ohs1
Nov 05, 2017 1:11:07 PM oracle.ohs.plugin.nodemanager.OhsRunCommand execute
INFO: Running /u02/oracle/middleware/oracle_home/wlserver/../ohs/bin/launch httpd -DOHS_MPM_EVENT -d /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1 -k start -f /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1/httpd.conf
Nov 05, 2017 1:11:07 PM oracle.ohs.plugin.nodemanager.OhsRunCommand runGeneric
INFO: Errors will be logged into /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/servers/ohs1/logs/ohs1.log
Nov 05, 2017 1:11:09 PM oracle.ohs.plugin.nodemanager.OhsRunCommand execute
INFO: /u02/oracle/middleware/oracle_home/wlserver/../ohs/bin/launch httpd -DOHS_MPM_EVENT -d /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1 -k start -f /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/config/fmwconfig/components/OHS/instances/ohs1/httpd.conf: exit status = 0
Nov 05, 2017 1:11:09 PM oracle.ohs.plugin.nodemanager.OhsProcessHandler buildProcess
INFO: Check the instance log file for more information: /u02/oracle/middleware/oracle_home/user_projects/domains/ohs_domain/servers/ohs1/logs/ohs1.log
<Nov 5, 2017 1:11:12 PM IST> <INFO> <ohs_domain> <ohs1> <The server 'ohs1' is running now.>
Successfully started server ohs1 ...