The crawler could not communicate with the server.

Question

valmiki

Answer 1

Hi,
According to your post, my understanding is that you get an error when communicating to the server.
  1.  This happens when crawler is not able to connect to the server. Make sure server name is correct and your crawl account should have the Full Read permission on the User Policy at the Web Application level.  It should not have any specific
permission on any site collection.
Couple of steps to troubleshoot it:
  a. You should be able to ping the server from the server having crawl component. Make sure there is an entry for the server in the host file under c:\Windows\System32\drivers\etc folder.
      Ping <servername>
  b.  You should be able to connect to the server using telnet command
      Telnet< servername> <port number>
https://social.technet.microsoft.com/Forums/en-US/01b6cdda-ca38-46c1-be07-2e89eb91271f/the-crawler-could-not-communicate-with-the-server-check-that-the-server-is-available-and-that-the?forum=sharepointsearchprevious
  2.  Can you browse to the WebApp from the server that is performing the Crawl? The issue is usually the most typical is the LoopBackCheck.
Click Start, click Run, type regedit, and then click OK.
In Registry Editor, locate and then click the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0
Right-click MSV1_0, point to New, and then click Multi-String Value.
Type BackConnectionHostNames, and then press ENTER.
Right-click BackConnectionHostNames, and then click  Modify.
In the Value data box, type the host name or the host names for the sites that are on the local  computer, and then click OK.
Quit Registry Editor, and then restart the IISAdmin service.
https://social.technet.microsoft.com/Forums/en-US/f378c45f-fa8b-48f3-88bb-739f3cd27830/the-crawler-could-not-communicate-with-the-server-check-that-the-server-is-available-and-that-the?forum=sharepointadminprevious
  3.  Checked WinProxy to see configured proxy:
       C:\Windows\system32>NetSH WinHTTP Show Proxy
       Run NetSH WinHTTP Reset Proxy
       Restart server and test again.
https://social.technet.microsoft.com/Forums/en-US/1baa6fd5-acc7-4cda-b7cb-7fa86aa8101f/the-crawler-could-not-communicate-with-the-server?forum=sharepointsearchprevious
  4.  The web.config file of the crawled web application contains an error.
       The target site collection contains a web part error for instance on the default.aspx.
       Also check the solution are not deployed correctly.Central Administration -> Solution Management (Manage Farm Solutions).
https://sharepointsriram.wordpress.com/2011/12/10/the-crawler-could-not-communicate-with-the-server-check-that-the-server-is-available-and-that-the-firewall-access-is-configured-correctly/
If the issue still exists, you can try to delete the old search application and recreate from the beginning.
You can also reset the index and do a full crawl after.
For more information about this similar issue, you can refer to:
http://sharepointroot.com/2012/03/16/sharepoint-search-the-crawler-could-not-communicate-with-the-server/
http://www.sharepointed.com/2013/08/13/the-crawler-could-not-communicate-with-the-server-check-that-the-server-is-available-and-that-the-firewall-access-is-configured-correctly/
http://www.information-worker.nl/2011/01/11/the-crawler-could-not-communicate-with-the-server/
https://social.technet.microsoft.com/Forums/en-US/0e7ffd07-c584-4767-a2bc-ce3a014255c6/the-crawler-could-not-communicate-with-the-server-check-that-the-server-is-available-and-that-the?forum=sharepointadminprevious
Best Regards,
Yumi Fu