Open a new Context to be used with a Socket. This function is a performance
variant of context(), designed to wrap a socket in a function argument when
calling request() or reply().
.context(socket)An external pointer.
a Socket.
External pointers created by this function are unclassed, hence methods for
contexts such as close() will not work (use reap() instead). Otherwise
they function identically to a Context when passed to all messaging
functions.