Recently tried to reinstall Sitecore 9.0 update 1 and got the following message:
"Request failed: Unable to connect to remote server" (and the URL which is default https://localhost:8389/solr)
![](/img/2018/03/sitecore-9-installer-unable-to-connect-to-remote-server/01_error.png)
Opening Solr in browser went well, and there were no existing cores that could prevent the installation. Weird...
![](/img/2018/03/sitecore-9-installer-unable-to-connect-to-remote-server/02_solr_working_well.png)
After experiments, I found out that was an antivirus preventing such requests. Disabling it allowed cores to be installed well and thу rest of install script succeeded.