Can't accept UDP connections java.net.BindException: Address already in use_解決方案

1、問題描述

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 在Linux服務器（CentOS7系統）中配置並啓動JMeter遠程監控服務器資源所需的ServerAgent目錄下的 startAgent.sh 文件時，系統出現異常提示，以下：

[root@fighter007 ServerAgent-2.2.1]# ./startAgent.sh INFO 2019-05-28 20:21:47.946 [kg.apc.p] (): Binding UDP to 4444 ERROR 2019-05-28 20:21:47.966 [kg.apc.p] (): Can't accept UDP connections
java.net.BindException: Address already in use at sun.nio.ch.Net.bind0(Native Method) at sun.nio.ch.Net.bind(Net.java:344) at sun.nio.ch.DatagramChannelImpl.bind(DatagramChannelImpl.java:672) at sun.nio.ch.DatagramSocketAdaptor.bind(DatagramSocketAdaptor.java:91) at kg.apc.perfmon.PerfMonWorker.listenUDP(PerfMonWorker.java:154) at kg.apc.perfmon.PerfMonWorker.startAcceptingCommands(PerfMonWorker.java:117) at kg.apc.perfmon.AgentTool.processParams(AgentTool.java:69) at kg.apc.cmdtools.PluginsCMD.processParams(PluginsCMD.java:63) at kg.apc.cmdtools.PluginsCMD.processParams(PluginsCMD.java:23) 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:601) at kg.apc.cmd.UniversalRunner.main(UniversalRunner.java:175) INFO 2019-05-28 20:21:47.967 [kg.apc.p] (): Binding TCP to 4444 ERROR 2019-05-28 20:21:47.970 [kg.apc.p] (): Can't accept TCP connections

2、問題分析

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 從以上拋出的異常信息中提取關鍵的提示信息：

"Can't accept UDP connections
java.net.BindException: Address already in use"

分析：ServerAgent默認開始的是4444端口，提示「不能接收UDP鏈接，地址已在使用中」，極可能是該端口已被佔用，須要修改成新的端口號再啓用or先暫停該端口對應的進程，而後再啓用ServerAgent服務

3、解決方案

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 方式1：先暫停4444端口，再啓用ServerAgent服務

查詢4444端口當前對應的進程：lsof -i:4444

[root@fighter007 ServerAgent-2.2.1]# lsof -i:4444 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME java 19720 root   19u  IPv6 129879       UDP *:krb524 java 19720 root   20u  IPv6 129880       TCP *:krb524 (LISTEN)

關閉指定PID號碼的進程（4444端口進程）：kill -9 104069

此時，亦可正常啓用ServerAgent服務，以下：

[root@fighter007 ServerAgent-2.2.1]# ./startAgent.sh INFO 2019-05-28 20:25:42.130 [kg.apc.p] (): Binding UDP to 4444 INFO 2019-05-28 20:25:43.169 [kg.apc.p] (): Binding TCP to 4444 INFO 2019-05-28 20:25:43.173 [kg.apc.p] (): JP@GC Agent v2.2.0 started

方式2：修改ServerAgent端口，再啓用ServerAgent服務

./startAgent.sh –udp-port 0 –tcp-port xxxx （"xxxx" 爲新端口號，如：4567） ./startAgent.sh –udp-port 0 –tcp-port 4567