ERROR source.NetcatSource: Unable to bind to socket. Exception follows.

环境： 使用flume端口监控策略的时候，中间自己多次启动退出Flume

问题： 一开始好好的，有一次莫名的就失败报错了

20/06/20 09:29:24 ERROR source.NetcatSource: Unable to bind to socket. Exception follows.
java.net.BindException: Cannot assign requested address
	at sun.nio.ch.Net.bind0(Native Method)
	at sun.nio.ch.Net.bind(Net.java:433)
	at sun.nio.ch.Net.bind(Net.java:425)
	at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
	at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
	at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:67)
	at org.apache.flume.source.NetcatSource.start(NetcatSource.java:164)
	at org.apache.flume.source.EventDrivenSourceRunner.start(EventDrivenSourceRunner.java:44)
	at org.apache.flume.lifecycle.LifecycleSupervisor$MonitorRunnable.run(LifecycleSupervisor.java:249)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
20/06/20 09:29:24 INFO source.NetcatSource: Source stopping
20/06/20 09:29:24 ERROR lifecycle.LifecycleSupervisor: Unable to start EventDrivenSourceRunner: { source:org.apache.flume.source.NetcatSource{name:r1,state:STOP} } - Exception follows.
org.apache.flume.FlumeException: java.net.BindException: Cannot assign requested address
	at org.apache.flume.source.NetcatSource.start(NetcatSource.java:171)
	at org.apache.flume.source.EventDrivenSourceRunner.start(EventDrivenSourceRunner.java:44)
	at org.apache.flume.lifecycle.LifecycleSupervisor$MonitorRunnable.run(LifecycleSupervisor.java:249)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.BindException: Cannot assign requested address
	at sun.nio.ch.Net.bind0(Native Method)
	at sun.nio.ch.Net.bind(Net.java:433)
	at sun.nio.ch.Net.bind(Net.java:425)
	at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
	at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
	at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:67)
	at org.apache.flume.source.NetcatSource.start(NetcatSource.java:164)
	... 9 more

问题分析： Cannot assign requested address 。主要是看到这个然后尝试着改了一下端口

解决方案： 端口被占用，当时是把端口号写为4444.基本上10000以上的端口是空闲的。所以把端口改为44444就可以了。