Why rsyslog show the error message "No UDP listen socket could successfully be initialized, message reception via UDP disabled."

Issue

• Why rsyslog show the error message "No UDP listen socket could successfully be initialized, message reception via UDP disabled."

• /var/log/messages file shows below error messages.

  • In RHEL8

    rsyslogd[10637]: No UDP socket could successfully be initialized, some functionality may be disabled.  [v8.1911.0-6.el8]
    rsyslogd[10637]: imudp: Could not create udp listener, ignoring port 67 bind-address (null). [v8.1911.0-6.el8]
    rsyslogd[10637]: imudp: no listeners could be started, input not activated.  [v8.1911.0-6.el8]
    rsyslogd[10637]: activation of module imudp failed [v8.1911.0-6.el8 try https://www.rsyslog.com/e/-3 ]
    

  • In RHEL7

    <syslog.err> rsyslogd:No UDP listen socket could successfully be initialized, message reception via UDP disabled.  [v8.24.0]
    <syslog.err> rsyslogd:imudp: no listeners could be started, input not activated.  [v8.24.0]
    <syslog.err> rsyslogd:activation of module imudp failed [v8.24.0 try http://www.rsyslog.com/e/-3 ]