easyasio is a cross-platform library uses asio for asynchronous TCP/UDP server/client. You can move from TCP to UDP/UDP to TCP without chaining your code at all, and it has connection pool/manager to handle clients connection/disconnection and messages
The Delphi WDosX Project Library (DWPL) is an Open Source
cross-platform library (based on FreeCLX) to make the development
of 32-bit DOS programs with Delphi (using WDOSX) flawless, and to make the
UI created with CLX available to DOS programs.