Editing Null modem (section)

=== Virtual null modem ===
A virtual null modem is a communication method to connect two [[application software|computer applications]] directly using a [[virtual serial port]]. Unlike a null modem cable, a virtual null modem is a [[software]] solution which emulates a hardware null modem within the computer.<ref>{{cite web |url=http://sourceforge.net/projects/com0com |title=Null-modem emulator &#124; Download Null-modem emulator software for free at |publisher=sourceforge.net |access-date=2013-12-26}}</ref><ref>{{cite web |url=http://developer.berlios.de/projects/n8vbvcomdriver/ |title=BerliOS Developer: Project Summary - N8VB_vCOM Virtual Null Modem Cable |publisher=berlios.de |date=2005-07-15 |access-date=2013-12-26 |url-status=dead |archive-url=https://web.archive.org/web/20131226111423/http://developer.berlios.de/projects/n8vbvcomdriver/ |archive-date=2013-12-26 }}</ref> All features of a hardware null modem are available in a virtual null modem as well. There are some advantages to this:
* Higher transmission speed of serial data, limited only by computer performance and network speed
* Virtual connections over local network or Internet, mitigating cable length restrictions
* Virtually unlimited number of virtual connections
* No need for a serial cable
* The computer's physical [[serial port]]s remain free

For instance, [[DOSBox]] has allowed older [[DOS]] games to use virtual null modems.

Another common example consists of Unix [[pseudoterminal]]s (pty) which present a standard [[Tty (Unix)|tty]] interface to user applications, including virtual serial controls. Two such ptys may easily be linked together by an application to form a virtual null modem communication path.