Proxy-Server is required, how deal with it?

[Tim Curtis]

I don't know whether the libcurl library which MPD uses picks up the environment variables but you could try something like below.

Create the file /etc/environment.d/10-proxy-server.conf containing the two lines below substituting your web proxy IP address and port.

export http_proxy="http://proxy-server-ip:port/"
export https_proxy="http://proxy-server-ip:port/"

Reboot and test