:- use_module(library(socket)). [semidet,multifile]try_proxy(+Proxy, 
+TargetAddress, -Socket, -StreamPair)
[semidet,multifile]try_proxy(+Proxy, 
+TargetAddress, -Socket, -StreamPair)library(http/http_open)) 
collect the results of failed proxies and raise an exception no proxy is 
capable of realizing the connection.
The default implementation recognises the values for Proxy 
described below. The library(http/http_proxy) adds
proxy(Host,Port) which allows for HTTP proxies using the
CONNECT method.