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The 27977 port socks proxies are pure socks5 proxy which only support socks5 protocol. IE (and Chrome) regards all the socks proxy as socks4 by default so IE can not use them.
Most socks5 proxies support both socks5 and socks4 protocol. They can be used as either socks5 or socks4 proxy. So IE can use other socks5 proxies but 27977 socks.
Firefox can set the version of the socks proxy so Firefox can use 27977 port proxies as well as curl.