RocketMQ—connect to 192.168.xxx.xxx:9876 failed

很多人在配置完毕之后两台RocketMQ的broker和nameserver都运行起来了，但是通过broker的日志发现一直报如下错误：

com.alibaba.rocketmq.remoting.exception.RemotingConnectException: connect to <192.168.140.128:9876> failed
	at com.alibaba.rocketmq.remoting.netty.NettyRemotingClient.invokeSync(NettyRemotingClient.java:641) ~[rocketmq-remoting-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.out.BrokerOuterAPI.registerBroker(BrokerOuterAPI.java:153) ~[rocketmq-broker-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.out.BrokerOuterAPI.registerBrokerAll(BrokerOuterAPI.java:193) ~[rocketmq-broker-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.BrokerController.registerBrokerAll(BrokerController.java:591) [rocketmq-broker-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.BrokerController$7.run(BrokerController.java:561) [rocketmq-broker-3.2.6.jar:na]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [na:1.7.0_79]
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304) [na:1.7.0_79]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178) [na:1.7.0_79]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.7.0_79]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_79]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_79]
	at java.lang.Thread.run(Thread.java:745) [na:1.7.0_79]
2018-06-10 21:22:25 INFO BrokerControllerScheduledThread1 - slave fall behind master, how much, 0 bytes
2018-06-10 21:22:26 INFO BrokerControllerScheduledThread1 - register broker to name server 192.168.140.129:9876 OK
2018-06-10 21:22:26 WARN BrokerControllerScheduledThread1 - registerBroker Exception, 192.168.140.128:9876
com.alibaba.rocketmq.remoting.exception.RemotingConnectException: connect to <192.168.140.128:9876> failed
	at com.alibaba.rocketmq.remoting.netty.NettyRemotingClient.invokeSync(NettyRemotingClient.java:641) ~[rocketmq-remoting-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.out.BrokerOuterAPI.registerBroker(BrokerOuterAPI.java:153) ~[rocketmq-broker-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.out.BrokerOuterAPI.registerBrokerAll(BrokerOuterAPI.java:193) ~[rocketmq-broker-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.BrokerController.registerBrokerAll(BrokerController.java:591) [rocketmq-broker-3.2.6.jar:na]
	at com.alibaba.rocketmq.broker.BrokerController$7.run(BrokerController.java:561) [rocketmq-broker-3.2.6.jar:na]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [na:1.7.0_79]
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304) [na:1.7.0_79]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178) [na:1.7.0_79]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.7.0_79]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_79]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_79]
	at java.lang.Thread.run(Thread.java:745) [na:1.7.0_79]

出现上述问题不用太慌，为什么呢，因为慌了你也解决不了啊……学好Linux还是相当重要的滴

首先要做几件事
1.相互之间ping一下看看能不能通;
2.ping一下外网看看能不能通(一般使用桥接模式);
    如果上述两个都通，那说明网络上应该是没什么问题的.

3.看看后台进程中是否有开启相应的服务，如果有9876端口，那就说明是正常的

netstat -ntlp

4.相互之间telnet一下

telnet 192.168.140.128 9876

如果未安装telnet，可以通过如下命令进行安装：

yum list telnet*    查看telnet相关的安装包
yum install telnet-server  安装telnet服务
yum install telnet.*  安装telnet客户端

一般情况出现上述错误这边telnet应该是不通的，原因是防火墙开着，我们需要将防火墙关闭.

1.firewall防火墙

（1）首先查看防火墙的状态

systemctl status firewalld

（2）如果防火墙开着，那么将其关闭

systemctl stop firewalld          

systemctl disable firewalld    #禁止firewall开机启动

2.iptables防火墙

这个很容易被忽视，或者是一不小心被打开，步骤依然如上

（1）先查看其状态

service iptables status

（2）如果开着将其关闭

service iptables stop                --临时关闭防火墙

chkconfig iptables off                    --永久关闭防火墙

经历了上述步骤，一般情况应该是没有问题，相互之间的接口调用应该是OK的，如果经历了上述步骤依然还没解决问题的，可以在博客底下评论，咱们可以一起探讨学习下