Com0com 64
Warning: For x64 versions of Windows (Vista, 7, 8+) a signed driver is required. The last com0com driver version signed available on SourceForge is the 2.2.2.0. A signed version of the latest com0com driver version 3.0.0.0 can be found at (files: setup_com0com_W7_x86_signed.exe and setup_com0com_W7_x64_signed.exe). It will automatically install a pair of virtual COM ports 'CNCA0' and 'CNCB0' that are linked by a virtual null modem cable. You can optionally change the names and edit the settings with the gui setup tool (setupg.exe). In this example they are named COM4 and COM5. IMPORTANT: After that, click on Apply.
Com0com 64
Windows will detect 'new hardware', click on Next and let Windows find and install the 'com0com serial emulator' hardware. You are done. Connecting the virtual machine and terminal application Connect the Virtual Machine to your first virtual port ('COM4') and the terminal application to the second ('COM5'). The properties of the serial port (usually specified in the virtual machine), like the baud rate, are not important. Instead, be sure to select 'NO FLOW CONTROL', because otherwise the terminal app won't receive any characters. What does com0com do? The virtual machine shows a COM1 port to ReactOS which is used for sending debug messages.