False java.net.BindException:地址已在Jetty上使用

在我的CI服务器上，我有一个测试需要启动Jetty服务器
测试如下：

1. 生成随机端口（使用合法TCP端口范围中的java rand）
2. 使用Linux的fuser进行验证，以检查该端口是否未使用
3. 运行测试

偶尔，即使在验证端口是空闲的之后，我也会得到异常：

WARN:oejuc.AbstractLifeCycle:FAILED SelectChannelConnector@0.0.0.0:49277 FAILED: java.net.BindException: Address already in use
java.net.BindException: Address already in use
    at sun.nio.ch.Net.bind0(Native Method)
    at sun.nio.ch.Net.bind(Net.java:444)
    at sun.nio.ch.Net.bind(Net.java:436)
    at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:214)
    at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
    at org.eclipse.jetty.server.nio.SelectChannelConnector.open(SelectChannelConnector.java:172)
    at org.eclipse.jetty.server.AbstractConnector.doStart(AbstractConnector.java:300)
    at org.eclipse.jetty.server.nio.SelectChannelConnector.doStart(SelectChannelConnector.java:249)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.server.Server.doStart(Server.java:272)
    at org.mortbay.jetty.plugin.JettyServer.doStart(JettyServer.java:65)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.mortbay.jetty.plugin.AbstractJettyMojo.startJetty(AbstractJettyMojo.java:511)
    at org.mortbay.jetty.plugin.AbstractJettyMojo.execute(AbstractJettyMojo.java:364)
    at org.mortbay.jetty.plugin.JettyRunWarMojo.execute(JettyRunWarMojo.java:71)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)

运行的测试：

• RHEL 6.3主机
• Maven 3.0.4
• jetty-maven插件：7.5.4
• Java 1.7.51

可能是什么原因？

谢谢！