The IBM WebSphere Host On-Demand Server, or HOD as it is commonly known is a Java application that runs on a Server that is deliverable via modern web servers such as the Apache web server. The application allows the end user to access IBM 3270, IBM 5250 and other Virtual terminals using the Telnet protocol whether through a secure or unsecured mode of communication. The product in its present form runs on AIX, UNIX, HP-UX, i5/OS, Z/OS, Linux, Solaris and Windows Server.
Delivery of the first web-based Telnet 3270, or TN3270 emulation adaptation is credited to Netscape Navigator a web browser designed by Netscape Communications Corporation. Telnet 3270, or TN3270 describes either the process of sending and receiving 3270 data streams using the Telnet protocol or the software that emulates a 3270 class terminal that communicates using that process. TN3270 allows a 3270 terminal emulator to communicate over a TCP/IP network instead of an SNA network. Standard telnet clients cannot be used as a substitute for TN3270 clients, as they use fundamentally different techniques for exchanging data. The Netscape versions offered limited functionality and essentially allowed web-based users to access the 3270 and UNIX, VAX and other computer host systems via the Netscape Navigator and Netscape Communicator web browser.
IBM Corporation in concert with Netscape Communications Corporation ultimately leveraged the popularity of the web-based host access for use with OS/2 and subsequent dissimilar computing operating systems. The second generation product was known as IBM Host On-Demand Version 1 through version 10.
IBM Websphere Host On-Demand provides access to IBM i (5250), IBM System z (3270), and DEC/UNIX systems through host screen emulation within the web browser. The connections are generally applied in a secure Internet environment using TLS, or SSL through the employment of Java's Virtual Machine.
IBM after acquiring Rational Software in 2003 and with Host On-Demand Version 11  changed the branding of Host On-Demand as a component of the IBM Rational Host Access Platform. Rational Host On-Demand allows for secure Web-to-host terminal emulation and host access application programming support with one interface to a TN3270E, TN5250, VT52, VT100, VT220, VT420, IBM CICS and FTP server access across multiple software operating systems and computing platforms.
Provides FIPS compliant, secure connectivity with TLS and SSL technologies and installs on a server, simplifying maintenance, distribution, and upgrades for system software. Host On-Demand also contains the necessary API's to allow creation of a custom portlet to access host applications from within IBM WebSphere Portal and additional programming operations from WebSphere Application Server.