Fixing: Sitecore 9 installer unable to connect to Solr server, while it is available
9 March 2018(0)
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)
Opening Solr in browser went well, and there were no existing cores that could prevent the installation. Weird...
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.