/usr/lib/swipl/library/socket.pl
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 tcp_connect(+Address, -StreamPair, +Options) is det
tcp_connect(+Socket, +Address, -StreamPair) is det
Establish a TCP communication as a client. The +,-,+ mode is the preferred way for a client to establish a connection. This predicate can be hooked to support network proxies. To use a proxy, the hook proxy_for_url/3 must be defined. Permitted options are:
bypass_proxy(+Boolean)
Defaults to false. If true, do not attempt to use any proxies to obtain the connection
nodelay(+Boolean)
Defaults to false. If true, set nodelay on the resulting socket using tcp_setopt(Socket, nodelay)

The +,+,- mode is deprecated and does not support proxies. It behaves like tcp_connect/4, but creates a stream pair (see stream_pair/3).

Errors
- proxy_error(tried(ResultList)) is raised by mode (+,-,+) if proxies are defines by proxy_for_url/3 but no proxy can establsh the connection. ResultList contains one or more terms of the form false(Proxy) for a hook that simply failed or error(Proxy, ErrorTerm) for a hook that raised an exception.
See also
- library(http/http_proxy) defines a hook that allows to connect through HTTP proxies that support the CONNECT method.