chromedriver missing command parameters when trying to start session via terminal

[ish...@gmail.com]

Hi Everyone,

I am trying to create a session using chromedriver and W3C WebDriver specification. The issue that I'm facing is that whenever I try to hit the /session endpoint I get the message "missing command parameters" as a response.

My Capabilities JSON :

{"browserName":chrome,"capabilities":{{"goog:chromeOptions":{"w3c":true,"debuggerAddress":"localhost: 52759"},"platform":MAC,"platformName":MAC,"version":74.0.3729.131}}}

Command & O/P :

ishabbi@Ishs-MacBook-Pro:~$ curl -v -XPOST "http://localhost:9515/session" -d '{"browserName":chrome,"capabilities":{{"goog:chromeOptions":{"w3c":true,"debuggerAddress":"localhost: 52759"},"platform":MAC,"platformName":MAC,"version":74.0.3729.131}}}'
Note: Unnecessary use of -X or --request, POST is already inferred.
* Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 9515 (#0)
> POST /session HTTP/1.1
> Host: localhost:9515
> User-Agent: curl/7.54.0
> Accept: */*
> Content-Length: 170
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 170 out of 170 bytes
< HTTP/1.1 400 Bad Request
< Content-Length:26
< Content-Type:text/plain
< Connection:close
<
* Closing connection 0
missing command parameters

Can anyone help me with the above request? I'm able to create sessions in geckodriver without any issues.

Thanks,
Ish

[John Chen]

The given JSON string has multiple errors, and isn't valid JSON syntax.

• Missing property name "alwaysMatch"
• Missing quotes at multiple places.
• W3C spec has no capabilities named "platform" or "version"

The following command should work:

curl -v -XPOST "http://localhost:9515/session" -d '{"capabilities":{"alwaysMatch":{"goog:chromeOptions":{"w3c":true,"debuggerAddress":"localhost: 52759"},"platformName":"MAC","browserVersion":"74.0.3729.131"}}}'

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[ish...@gmail.com]

On Thursday, May 2, 2019 at 10:00:47 PM UTC+5:30, John Chen wrote:
> The given JSON string has multiple errors, and isn't valid JSON syntax.

> Missing property name "alwaysMatch"Missing quotes at multiple places.W3C spec has no capabilities named "platform" or "version"

Hello John,

I tried the command that you shared. This time I face a different issue, I get the below error repeatedly until the request timeouts :

[1556856404.661][DEBUG]: DevTools HTTP Request: http://localhost:52759/json/version
[1556856404.662][DEBUG]: DevTools HTTP Request failed

Any idea?

[John Chen]

Most likely you don't have a Chrome listening at port 52759. Did you start Chrome with --remote-debugging-port=52759 on the command line?

Direct communication with ChromeDriver through W3C protocol is not recommended for normal usage. Have you tried using Selenium library from https://www.seleniumhq.org/download/?

[ish...@gmail.com]

I just started the chromedriver and proceeded to execute the HTTP request.

I've been using Selenium library in the day to day needs. I just want to know more on the internals of the WebDriver and if possible contribute. Hence, checking things out :-)

[John Chen]

By including debuggerAddress in chromeOptions, the command is telling ChromeDriver not to start Chrome, but instead just connect to an existing Chrome on port 52759. Unless you actually have a Chrome listening at that port, the communication won't work.

[ish...@gmail.com]

It works now John! Thanks a lot! :-)