TCP Port Toolkit is a protocol, data, and timing analyzer.
COM Port Stress Test is a tool for testing a COM or RS232 port (device).
It is also a very handy utility during your LPT port development activities.
Simple Port Tester is a neat application created to test TCP and UDP ports.
List available hosts, open ports, and their characteristics.
HW Virtual Serial Port allows creating virual serial port drivers.
VSPE is intended for engineers and developers to create/debug/test applications.
Process And Port Analyzer is a packet viewer and sniffer.
B&W Port Scanner is a program that will scan your TCP ports.
Serial Port Tool
Professional debug tool for serial port, TCP/IP, UDP, I2C, HTTP communication.
Flachmann & Heggelbacher
Establishes TCP connections, accepts a TCP connection on a local port, etc.
The dialer uses one local UDP port and one local TCP port.
NetworkActiv AUTAPF is a UDP and TCP port forwarder.
TCP/IP port redirector with many features for the advanced user.
Knocker is a simple and easy to use TCP security port scanner.
A multi-threaded and fast TCP port scanner.
Coral Works, Inc.
Software-based TCP/IP port forwarder and network administration service.
A powerful connect-based TCP port scanner, pinger and hostname resolver. Multithreaded and asynchron....
Free, unrestricted Virtual Serial Port driver for any TCP/IP devices.