Selenium Grid 3.4.0 node cannot connect hub

i installed selenium-server-standalone-3.4.0.jar and run following command(as hube) on my machine A:

java -jar selenium-server-standalone-3.4.0.jar

it runs successfuly.

then, on my machine B(as node) run following command:

java -jar selenium-server-standalone-3.4.0.jar -role node -hub http://ift.tt/2uMBRod

following logs produced. As you can see see, first it registered then it indicates it is not registered. How could be possible?

11:35:29.561 INFO - Selenium build info: version: '3.4.0', revision: 'unknown' 11:35:29.562 INFO - Launching a Selenium Grid node 11:35:30.353 WARN - error getting the parameters from the hub. The node may end up with wrong timeouts.com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 12 path $ 2017-07-23 11:35:30.417:INFO::main: Logging initialized @1343ms to org.seleniumhq.jetty9.util.log.StdErrLog 11:35:30.568 INFO - Driver provider org.openqa.selenium.ie.InternetExplorerDriver registration is skipped: registration capabilities Capabilities [{ensureCleanSession=true, browserName=internet explorer, version=, platform=WINDOWS}] does not match the current platform LINUX 11:35:30.568 INFO - Driver provider org.openqa.selenium.edge.EdgeDriver registration is skipped: registration capabilities Capabilities [{browserName=MicrosoftEdge, version=, platform=WINDOWS}] does not match the current platform LINUX 11:35:30.572 INFO - Driver class not found: com.opera.core.systems.OperaDriver 11:35:30.572 INFO - Driver provider com.opera.core.systems.OperaDriver registration is skipped: Unable to create new instances on this machine. 11:35:30.573 INFO - Driver class not found: com.opera.core.systems.OperaDriver 11:35:30.575 INFO - Driver provider com.opera.core.systems.OperaDriver is not registered 11:35:30.585 INFO - Driver provider org.openqa.selenium.safari.SafariDriver registration is skipped: registration capabilities Capabilities [{browserName=safari, version=, platform=MAC}] does not match the current platform LINUX 2017-07-23 11:35:30.729:INFO:osjs.Server:main: jetty-9.4.3.v20170317 2017-07-23 11:35:30.828:INFO:osjsh.ContextHandler:main: Started o.s.j.s.ServletContextHandler@70be0a2b{/,null,AVAILABLE} 2017-07-23 11:35:30.899:INFO:osjs.AbstractConnector:main: Started ServerConnector@29176cc1{HTTP/1.1,[http/1.1]}{0.0.0.0:5555} 2017-07-23 11:35:30.900:INFO:osjs.Server:main: Started @1827ms

11:35:30.900 INFO - Selenium Grid node is up and ready to register to the hub

11:35:31.017 INFO - Starting auto registration thread. Will try to register every 5000 ms.

11:35:31.017 INFO - Registering the node to the hub: http://ift.tt/2uoddYj

11:35:31.062 INFO - The node is registered to the hub and ready to use

11:35:36.095 INFO - Couldn't register this node: The hub is down or not responding: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 12 path $ 11:35:41.123 INFO - Couldn't register this node: The hub is down or not responding: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 12 path $ 11:35:46.135 INFO - Couldn't register this node: The hub is down or not responding: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 12 path $