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

一、问题描述

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在Linux服务器（CentOS7系统）中配置并启动JMeter远程监控服务器资源所需的ServerAgent目录下的 startAgent.sh 文件时，系统出现异常提示，如下：

[root@fighter007 ServerAgent-2.2.]# ./startAgent.sh
INFO    -- ::47.946 [kg.apc.p] (): Binding UDP to
ERROR   -- ::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:)
    at sun.nio.ch.DatagramChannelImpl.bind(DatagramChannelImpl.java:)
    at sun.nio.ch.DatagramSocketAdaptor.bind(DatagramSocketAdaptor.java:)
    at kg.apc.perfmon.PerfMonWorker.listenUDP(PerfMonWorker.java:)
    at kg.apc.perfmon.PerfMonWorker.startAcceptingCommands(PerfMonWorker.java:)
    at kg.apc.perfmon.AgentTool.processParams(AgentTool.java:)
    at kg.apc.cmdtools.PluginsCMD.processParams(PluginsCMD.java:)
    at kg.apc.cmdtools.PluginsCMD.processParams(PluginsCMD.java:)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:)
    at java.lang.reflect.Method.invoke(Method.java:)
    at kg.apc.cmd.UniversalRunner.main(UniversalRunner.java:)
INFO    -- ::47.967 [kg.apc.p] (): Binding TCP to
ERROR   -- ::47.970 [kg.apc.p] (): Can't accept TCP connections

二、问题分析

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从以上抛出的异常信息中提取关键的提示信息：

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

分析：ServerAgent默认开始的是4444端口，提示“不能接收UDP连接，地址已在使用中”，很可能是该端口已被占用，需要修改为新的端口号再启用or先暂停该端口对应的进程，然后再启用ServerAgent服务

三、解决方案

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方式1：先暂停4444端口，再启用ServerAgent服务

查询4444端口当前对应的进程：lsof -i:4444

[root@fighter007 ServerAgent-2.2.]# lsof -i:
COMMAND   PID USER   FD   TYPE DEVICE SIZE NODE NAME
java     root   19u  IPv6        UDP *:krb524
java     root   20u  IPv6        TCP *:krb524 (LISTEN)

关闭指定PID号码的进程（4444端口进程）：kill -9 104069

此时，亦可正常启用ServerAgent服务，如下：

[root@fighter007 ServerAgent-2.2.]# ./startAgent.sh
INFO    -- ::42.130 [kg.apc.p] (): Binding UDP to
INFO    -- ::43.169 [kg.apc.p] (): Binding TCP to
INFO    -- ::43.173 [kg.apc.p] (): JP@GC Agent v2.2.0 started

方式2：修改ServerAgent端口，再启用ServerAgent服务

./startAgent.sh –udp-port  –tcp-port xxxx （"xxxx" 为新端口号，如：）
./startAgent.sh –udp-port  –tcp-port