Why Does a Client Fail to Connect to a RabbitMQ Instance?

Possible Cause 1: Incorrect Connection Address

Error message displayed when an incorrect connection address is used during intra-VPC access:

[root@ecs-test RabbitMQ-Tutorial]# java -cp .:rabbitmq-tutorial.jar Send 192.168.125.110 5672 user *******
Exception in thread "main" java.net.NoRouteToHostException: No route to host (Host unreachable)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)

Error message displayed when an incorrect connection address is used during public access:

[root@ecs-test RabbitMQ-Tutorial]# java -cp .:rabbitmq-tutorial.jar Send 139.xxx.178 5672 user *******
Exception in thread "main" java.net.SocketTimeoutException: connect timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)

Solution: On the Basic Information page of the RabbitMQ console, obtain the private or public network connection address and modify the connection address in the code.

Possible Cause 2: Incorrect Port

Error message displayed when an incorrect port is used during intra-VPC access:

[root@ecs-test RabbitMQ-Tutorial]# java -cp .:rabbitmq-tutorial.jar Send 192.168.125.111 5673 user *******
Exception in thread "main" java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)

Error message displayed when an incorrect port is used during public access:

[root@ecs-test RabbitMQ-Tutorial]# java -cp .:rabbitmq-tutorial.jar Send 139.xxx.179 5673 user *******
Exception in thread "main" java.net.SocketTimeoutException: connect timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)

Solution: Change the port number.

Possible Cause 3: Incorrect Username or Password

The error information is as follows:

[root@ecs-test RabbitMQ-Tutorial]# java -cp .:rabbitmq-tutorial.jar Send 192.168.125.111 5672 user *******
Exception in thread "main" com.rabbitmq.client.AuthenticationFailureException: ACCESS_REFUSED - Login was refused using authentication mechanism PLAIN. For details
 see the broker logfile.
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:351)
at com.rabbitmq.client.impl.recovery.RecoveryAwareAMQConnectionFactory.newConnection(RecoveryAwareAMQConnectionFactory.java:64)

Solution: Change the username or password. If you forget the password, set a new one by referring to Resetting the Instance Password.

Possible Cause 4: Maximum Number of Connections Exceeded

The error information is as follows:

Solution: Close unused connections.

Possible Cause 5: No Virtual Host Available or Incorrect Virtual Host Name

The error information is as follows:

Couldn't log in: server connection error 530, message: NOT_ALLOWED - vhost /localdev/ not found

Solutions:

• If no virtual host is available, go to the Virtual Hosts page of the RabbitMQ console and create one.
• If the virtual host name is incorrect, modify the connection URL and configuration file according to the virtual host name displayed on the Virtual Hosts page of the RabbitMQ console.