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Telnet (cisco_ios_telnet) via SOCKS5 proxy timing out

See original GitHub issue

Trying to Telnet to a Cisco switch via a SOCKS5 proxy, the connection always times out.

Code used to connect:

sock_proxy_telnet = socks.socksocket()
sock_proxy_telnet.set_proxy(
	proxy_type=socks.SOCKS5,
	addr="192.160.1.50",
	port=1080
)
sock_proxy_telnet.connect(('192.168.140.10', 23))
net_connect = ConnectHandler(
	host='192.168.140.10',
	device_type="cisco_ios_telnet",  # Use Telnet instead.
	username='my_username',
	password='my_password',
	fast_cli=False,
	sock=sock_proxy_telnet
)
show_version = net_connect.send_command('sh ver')

It sits on the ConnectHandler and times out, error:

[WinError 10060] A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond

I’ve confirmed that the socket is connecting via sock_proxy_telnet.recv(1000) (shows the login banner).

The above code works fine if I use port 22 on the .connect and cisco_ios on the device type. I tried to debug it, but the global logging method doesn’t generate any logs.

I can use PuTTy to connect via the SOCKS5 proxy and Telnet, so I think this is specific to how Netmiko handles the socket and Telnet.

Any help would be greatly appreciated.