Tools

Internet Direct (Indy)
An open source internet component suite comprised of popular internet protocols that is included in both Delphi 6 and Kylix. Both client and server implementations are included as well as full source code and demos.
http://www.indyproject.org/

Listen
Utilizes standard Windows COM port drivers to tap into RS-232 transmit signals for monitoring bi-directional communications between two devices. (WinTECH Software)
http://www.win-tech.com/html/listen.htm

SocketWrench
Toolkit for Internet software development, from Catalyst.
http://www.catalyst.com/products/socketwrench/

SocktSpy
Provides tracing capabilities for the WinSock API calls. (WinTECH Software)
http://www.win-tech.com/html/socktspy.htm

TracePlus32 Web Detective
HTTP Trace/Debug and data analysis tools for Win32. (Systems Software Technology, Inc.)
http://www.sstinc.com/webanal.html

TracePlus/Win32
Win32 API trace/debugger spy for Windows 95/98/NT/2000. It monitors kernel, DDE, ODBC, COM, OLE, registry, serial, shell, MAPI, TAPI, Internet, window related APIs. (Systems Software Technology, Inc.)
http://www.sstinc.com/windows.html

TracePlus/Winsock
WinSock Trace/Debug and data analysis tools for Win32. (Systems Software Technology, Inc.)
http://www.sstinc.com/winsock.html