Usually this indicates some sort of network problem. That can be because there's a problem somewhere beyond your computer, or it can be because there's a problem on your computer itself.
Oftentimes these problems are caused by a proxy, a third-party antivirus or firewall, or other programs which monitor or intercept network traffic. These services can for many reasons try to terminate connections, leading to this result.
If you're using a proxy, try switching to a network without it. If you're using a third-party antivirus, firewall, or other program intercepting network traffic, try uninstalling it completely and restarting. If this isn't possible in your environment, contact your IT department about the problem, and tell them that you believe that software is preventing your from doing your job.
If you've done all of these and none of them help, you may want to contact your ISP to see if there's a network problem on your connection.
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