This error is thrown after Sending GET request to server. The URL is configured to something like http://localhost:50955/xxx?id=x via HTTP client connector.
If the HTTP service is hosted on the same machine on which the atom is running, configure the HTTP client connector as follows:
HTTP Client Connection:
Use localhost instead of machine's host name since the web service is running on the same machine where the atom is installed. Make sure port 50955 is configured under Atom--> Shared Web Server Settings.
HTTP Client Operation:
Connector Action : Send
Select Request Profile Type: None
Select Response Profile Type: None
Content Type : text/plain
HTTP method : POST
Save the connector configuration and re-test the process.