Appears to me that WinSock unit does not have an StreamLn function (as PowerSock's PSock.pas unit uses Winsock as imported unit).
The StreamLn function in PSock.pas just adds an CRLF sequence to the string passed as parameter before calling the TStream.WriteBuffer method of the passed TStream parameter.
Here's the google cache snapshot from the Powersock's source code of PSock.pas
