What function would you use to open a socket connection manually with the purpose of communicating with a server not supported by a file wrapper?
fsockopen
Correct:
fsockopen
You would normally use the fsockopen function to open a socket connection for communicating with a server whose protocol is not supported by PHP. This is useful, say, for communicating with a server that uses its own protocol and can be combined with userdefined file wrappers to implement stream support in PHP.