In case when logging to syslog through UDP protocol is configured and syslog port becomes unreachable then after syslog restart first message can be thrown away. It happens when odd number of messages are attempted to be logged during syslog is unreachable. In is caused when port unreachable is returned during logging attempt, then another log attempt automatically fail even is syslog server has been started meanwhile.

How to reproduce:
1) Configure EAP to log some category to syslog through UDP:
            <syslog-handler name="SYSLOG">
                <server-address value="127.0.0.1"/>
                <hostname value="-"/>
                <port value="10514"/>
                <app-name value="JBossEAP"/>
                <formatter>
                    <syslog-format syslog-type="RFC5424"/>
                </formatter>
                <facility value="local-use-5"/>
            </syslog-handler>
...
            <logger category="org.jboss.as.test.integration.logging.operations">
                <level name="INFO"/>
                <handlers>
                    <handler name="SYSLOG"/>
                </handlers>
            </logger>

2) Start application server and syslog server.
3) Deploy logging servlet (see attachements) which makes one log when is accessed.
4) Access http://127.0.0.1:8080/logging-deployment/logger -> message is logged to syslog
5) Stop Syslog server
6) Access http://127.0.0.1:8080/logging-deployment/logger 0, 2, 4 times... (message is not logged to syslog since it is down)
7) Start Syslog server
8) Access http://127.0.0.1:8080/logging-deployment/logger -> message is logged to syslog (correct behavior)
9) Stop Syslog server
10) Access http://127.0.0.1:8080/logging-deployment/logger 1, 3, 5 times... (message is not logged to syslog since it is down)
11) Start Syslog server
12) Access http://127.0.0.1:8080/logging-deployment/logger -> message is NOT logged to syslog (wrong behavior)
13) Access http://127.0.0.1:8080/logging-deployment/logger again -> message is logged to syslog