Eltima Serial Port Monitor
Serial Port Monitor is a professional application for RS232/422/485 COM ports monitoring. It monitors, displays, logs and analyzes all serial port activity in a system. It can effectively be used for monitoring serial data exchange between serial devices and any Windows application, debugging... Serial Port Monitor supports all COM-port types: standard on-board ports, extension board ports, SERIAL-via-USB adapters. ... Serial Port Monitor is a powerful system utility for exploring the way OS works, monitoring how applications use ports, for tracking down problems in system or application...
http://www.mks.zp.ua/serial_port_monitor.exe - 3Mb - Download - Screenshot

AVSD OEM
AVSD OEM is a programming interface, which allows you to add support of virtual serial ports to your own application. You have full control over ports created with the help of AVSD OEM, including reading data that some other application has written using WriteFile function, writing data to be... Now you can monitor all data that application writes to the port and redirect it to the real COM port. ... If you have the software, which works with some device connected to COM port and you want to capture all the data that goes to and from the port, then AVSD OEM is what you need!
http://www.virtualserialdriver.com/files/avsd_oem.zip - 448Kb - Download

Multicom OEM
Multicom OEM is a programming interface, which allows you to add support of virtual serial ports to your own application. You have full control over ports created with the help of Multicom OEM, including reading data that some other application has written using WriteFile function, writing data... Now you can monitor all data that application writes to the port and redirect it to the real COM port. ... If you have the software, which works with some device connected to COM port and you want to capture all the data that goes to and from the port, then Multicom OEM is what you need!
http://www.intellidriver.com/downloads/products/multicomoem.zip - 448Kb - Download

Serial Port Monitoring Control
Serial Port Monitoring Control (SPMC) - RS232 Data Acquisition and Com Port Control Component Library, Modem Access Component. Connection Sniffer and Port Test Software Library. The library lets you enumerate all installed serial devices, including, but not limited to serial ports and modems. ... The Monitor object can be attached to the device at any time, no matter if the device is being currently used or not. ... After you get an instance of the serial device, you can create a monitor object and attach to the device to receive monitored data and events.
http://www.hhdsoftware.com/Download/hhdspmc.exe - 470Kb - Download - Screenshot

Advanced Virtual COM Port
Advanced Virtual COM Port is the first software of its kind which includes both local and network virtual COM port functions. It can share your real COM ports or it can create virtual COM ports and connect them with a virtual null-modem cable locally or through a TCP/IP network or the Internet. ... You can connect to a shared port and use it just like it is on your machine. ... Virtual serial ports created by the program look and work the same way as real ones look and work.
http://www.advancedvirtualcomport.com/files/AdvancedVirtualComPort.zip - 1Mb - Download - Screenshot

Free Serial Port Monitor
Free software serial port monitor, Com Rs232 sniffer with communication packet data analyzer. This monitoring utility can spy, capture, view, analyze, test com ports activity performing com port connection and traffic analysis with data acquisition and control. ... Free Serial Port Monitor can be successfully used by programmers, beta-testers, software developers, hardware engineers, IT support specialists, industrial control personnel, SCADA software engineers, science technicians, systems integrators, consultants, lab experts, University students.
http://www.serial-port-monitor.com...load/free-serial-port-monitor.exe - 3Mb - Download - Screenshot

Serial Port Sniffer ActiveX Control
Serial Port Sniffer is a powerful advanced ActiveX Control that allows your application to sniff (fully monitor and edit data flows) serial port in your system. Serial Port Sniffer ActiveX Control detects all serial port activity in your system, all applications that work with serial port and... Some of the features are: Allows to monitor and edit serial data streams directly from your application; Unique ActiveX Control - no need to use additional software for monitoring; Wide selection of supported events, methods and properties; Control lines support (DTR, RTS, CTS, RTS); No reboot...
http://www.serial-port-communication.com/download/spsax_demo.exe - 2Mb - Download - Screenshot

Fast Port Scanner
Fast Port Scanner is a fast multithreaded port scanner that scans about 400 ports a second. It supports both the TCP/IP and UDP protocols. You can select address ranges to scan multiple interfaces or hosts. Any open ports will have the any suspect Trojans listed with it. ... This program is free when using Global Up Time website monitoring service.
http://www.globalwebmonitor.com/software/FastScannerSetup.exe - 636Kb - Download - Screenshot

Serial Monitor
Software serial port monitor Rs232 sniffer with protocol analyzer and packet data logger. This monitoring utility can spy, capture, view, log, analyze, test com ports activity performing com port connection and traffic analysis with data acquisition and control. ... Serial Monitor can be successfully used for monitoring data flow between serial devices and Windows application, debugging com port connections, developing, reverse-engineering and implementing serial protocol, serial device driver development, serial hardware development, research the functionality of any third-party software...
http://www.hhdsoftware.com/Download/serial-monitor.exe - 1Mb - Download - Screenshot

Smart Sniffer(former Multi Ports Sniffer for COM, LPT, USB).
The best tool for doing LPT, COM and USB port's data transfer logging. Using this tool you can simply do monitoring and spying data transffered through ports. This is useful for people who want to research any additional HW connected to port like mobile phones.
http://www.smartsniff.com/cgi-bin/gets.pl - 2Mb - Download - Screenshot