"Exception: Unable to find a free port" - SeGrid/Python/Chromedriver/Ubuntu+OSX

Short Description: on attempting to execute parallel tests on a host using selenium grid, the server-standalone hub accepts the first session and rejects all subsequent requests to create a session until the first terminates.

Longer Description: I am not a java developer, so I can only dig so deeply, but it does look like something is not being correctly executed in the PortProber.java class. However, it may be something to do with the python requests to create a new session. I spent some time digging into the python code and wasn’t able to find a way to force a particular port be requested for the new session.

We’re trying to run multiple scripts on a headless virtual. This pattern has worked previously, but we needed to make updates to our chrome version, so we went ahead and updated the selenium-standalone version (I’ve tried 2.49-2.52), chromedriver (2.20-2.21), and Chrome (48.0.2564.82). In fact, in developing the python test script, I was able to run 4 sessions simultaneously on my OSX laptop. That is no longer the case (server standalone 2.50/2.52 tried - 2.50 previously worked)

I did try the selenium-server-standalone + a quick webdriver.io (nodeJS) script and it appears to work on my laptop.

Script to recreate: (start one instance, then start another on the same system)

#test.py
from selenium import webdriver
import time

baseURL='http://www.yahoo.com'
url2='http://www.bing.com'

options=webdriver.ChromeOptions()
options.add_argument('--disable-logging')
driver=webdriver.Remote(desired_capabilities=options.to_capabilities())

driver.get(baseURL)
time.sleep(2.5)
print(driver.title)

driver.get(url2)
time.sleep(2.5)
print(driver.title)

driver.get(baseURL)
time.sleep(2.5)
print(driver.title)

driver.get(url2)
time.sleep(2.5)
print(driver.title)

driver.close()
driver.quit()

Python Script Error:

>>>python test.py
Traceback (most recent call last):
  File "test.py", line 11, in <module>
    driver=webdriver.Remote(desired_capabilities=options.to_capabilities())
  File "/usr/local/lib/python2.7/dist-packages/selenium-2.51.1-py2.7.egg/selenium/webdriver/remote/webdriver.py", line 87, in __init__
    self.start_session(desired_capabilities, browser_profile)
  File "/usr/local/lib/python2.7/dist-packages/selenium-2.51.1-py2.7.egg/selenium/webdriver/remote/webdriver.py", line 141, in start_session
    'desiredCapabilities': desired_capabilities,
  File "/usr/local/lib/python2.7/dist-packages/selenium-2.51.1-py2.7.egg/selenium/webdriver/remote/webdriver.py", line 201, in execute
    self.error_handler.check_response(response)
  File "/usr/local/lib/python2.7/dist-packages/selenium-2.51.1-py2.7.egg/selenium/webdriver/remote/errorhandler.py", line 193, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.WebDriverException: Message: Unable to find a free port

selenium-standalone-server error output:

10:59:41.649 INFO - Executing: [new session: Capabilities [{platform=ANY, javascriptEnabled=true, browserName=chrome, chromeOptions={args=[--disable-logging], extensions=[]}, version=}]])
10:59:41.650 INFO - Creating a new session for Capabilities [{platform=ANY, javascriptEnabled=true, browserName=chrome, chromeOptions={args=[--disable-logging], extensions=[]}, version=}]
10:59:41.652 WARN - Exception thrown
java.util.concurrent.ExecutionException: org.openqa.selenium.WebDriverException: java.lang.reflect.InvocationTargetException
Build info: version: '2.52.0', revision: '4c2593c', time: '2016-02-11 19:06:42'
System info: host: '**************', ip: '************', os.name: 'Linux', os.arch: 'amd64', os.version: '3.16.0-43-generic', java.version: '1.7.0_91'
Driver info: driver.version: unknown
  at java.util.concurrent.FutureTask.report(FutureTask.java:122)
  at java.util.concurrent.FutureTask.get(FutureTask.java:188)
  at org.openqa.selenium.remote.server.DefaultSession.execute(DefaultSession.java:183)
  at org.openqa.selenium.remote.server.DefaultSession.<init>(DefaultSession.java:119)
  at org.openqa.selenium.remote.server.DefaultSession.createSession(DefaultSession.java:95)
  at org.openqa.selenium.remote.server.DefaultDriverSessions.newSession(DefaultDriverSessions.java:124)
  at org.openqa.selenium.remote.server.handler.NewSession.handle(NewSession.java:59)
  at org.openqa.selenium.remote.server.handler.NewSession.handle(NewSession.java:1)
  at org.openqa.selenium.remote.server.rest.ResultConfig.handle(ResultConfig.java:111)
  at org.openqa.selenium.remote.server.JsonHttpCommandHandler.handleRequest(JsonHttpCommandHandler.java:79)
  at org.openqa.selenium.remote.server.DriverServlet.handleRequest(DriverServlet.java:202)
  at org.openqa.selenium.remote.server.DriverServlet.doPost(DriverServlet.java:164)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
  at org.openqa.selenium.remote.server.DriverServlet.service(DriverServlet.java:130)
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
  at org.openqa.jetty.jetty.servlet.ServletHolder.handle(ServletHolder.java:428)
  at org.openqa.jetty.jetty.servlet.ServletHandler.dispatch(ServletHandler.java:680)
  at org.openqa.jetty.jetty.servlet.ServletHandler.handle(ServletHandler.java:571)
  at org.openqa.jetty.http.HttpContext.handle(HttpContext.java:1526)
  at org.openqa.jetty.http.HttpContext.handle(HttpContext.java:1479)
  at org.openqa.jetty.http.HttpServer.service(HttpServer.java:920)
  at org.openqa.jetty.http.HttpConnection.service(HttpConnection.java:820)
  at org.openqa.jetty.http.HttpConnection.handleNext(HttpConnection.java:986)
  at org.openqa.jetty.http.HttpConnection.handle(HttpConnection.java:837)
  at org.openqa.jetty.http.SocketListener.handleConnection(SocketListener.java:243)
  at org.openqa.jetty.util.ThreadedServer.handle(ThreadedServer.java:358)
  at org.openqa.jetty.util.ThreadPool$PoolThread.run(ThreadPool.java:537)
Caused by: org.openqa.selenium.WebDriverException: java.lang.reflect.InvocationTargetException
Build info: version: '2.52.0', revision: '4c2593c', time: '2016-02-11 19:06:42'
System info: host: '**********', ip: '**********', os.name: 'Linux', os.arch: 'amd64', os.version: '3.16.0-43-generic', java.version: '1.7.0_91'
Driver info: driver.version: unknown
  at org.openqa.selenium.remote.server.DefaultDriverProvider.callConstructor(DefaultDriverProvider.java:113)
  at org.openqa.selenium.remote.server.DefaultDriverProvider.newInstance(DefaultDriverProvider.java:97)
  at org.openqa.selenium.remote.server.DefaultDriverFactory.newInstance(DefaultDriverFactory.java:60)
  at org.openqa.selenium.remote.server.DefaultSession$BrowserCreator.call(DefaultSession.java:222)
  at org.openqa.selenium.remote.server.DefaultSession$BrowserCreator.call(DefaultSession.java:1)
  at java.util.concurrent.FutureTask.run(FutureTask.java:262)
  at org.openqa.selenium.remote.server.DefaultSession$1.run(DefaultSession.java:176)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
  at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
  at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
  at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
  at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
  at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
  at org.openqa.selenium.remote.server.DefaultDriverProvider.callConstructor(DefaultDriverProvider.java:103)
  ... 9 more
Caused by: java.lang.RuntimeException: Unable to find a free port
  at org.openqa.selenium.net.PortProber.findFreePort(PortProber.java:67)
  at org.openqa.selenium.remote.service.DriverService$Builder.build(DriverService.java:292)
  at org.openqa.selenium.chrome.ChromeDriverService.createDefaultService(ChromeDriverService.java:88)
  at org.openqa.selenium.chrome.ChromeDriver.<init>(ChromeDriver.java:138)
  ... 14 more
10:59:41.658 WARN - Exception: Unable to find a free port

[visionscaper]

I had exactly the same exception in the selenium-standalone-server error output. It turned out that I had statements in my /etc/hosts file that I had to remove (or comment out), e.g.

127.0.0.1 my-site.local

...

192.168.100.48 localhost   

[DavidGDD]

I have the same problem running on Linux. So after reading the responses and a week thinking that the problem was in my localhost definition or webdriver/driver/selenium versions, i’ve read the PortProber.java and LinuxEphemeralPortRangeDetector.java. There is a case in createAcceptablePort in which is always returning the same port, not random.

When you have defined in the “/proc/sys/net/ipv4/ip_local_port_range” the port range 1024-65535, the method returns always 1024. So if you change your range defined in the file to 1025-65535 (or whatever) it will work returning random ports.