Appendix I. GPORT Application Modes
1. Expanding the number of serial ports of the mainframe
Usually, mainframes (Unix mainframes or common PC) incorporate only a
limited number of serial ports themselves. However, many applications require a
large number of serial ports to get connected with multiple serial port equipment
and to enable the mainframes to control this equipment. Sometimes the number of
serial ports required may reach as high as a few hundred.
Multi-serial port card is one solution to expand the number of mainframe
serial ports. Multi- user cards are inserted into the expansion slots (PCI and ISA)
of the mainframes directly. With multi- serial port card driving programs, this
method can increase the number of the mainframe serial ports. Developers and
users may operate these expanded serial ports the way they operate ordinary
serial ports. Simple as the method is, it has a lot of vulnerabilities. First, the
number of expandable serial ports is limited. Currently, multi- user cards in the
market can incorporate 64 serial ports at most, which is not enough to meet the
requirement of some applications. Second, considerable weaknesses exist in the
maintenance, function and cable of multi-serial port cards.
Serial port equipment server is another solution to expand the number of
mainframe serial ports. Serial port equipment servers can be connected with the
mainframes through random physical connection, given that both have TCP/IP
connections. Serial port equipment can be connected with serial port equipment
servers directly or through modems and other devices. Under this circumstance, it
is also necessary that the mainframes incorporate driving programs to enable
mainframes to visit these ports whose physical positions are at the serial port
equipment servers, just as they visit ordinary serial ports. Compared with the case
of multi- serial port cards, the number of expandable serial ports is basically
unlimited here, reaching up to a few hundreds easily. Besides, the advantages are
obvious over multi-serial port card in terms of system maintenance, upgrade,
function and cable.
It is worth mentioning that both multi-serial port card and serial port
equipment servers need to provide mainframe-driving programs to expand serial
ports in the mainframe. In view of the numerous types of the mainframes and the
status in the current domestic market, the following mainframe driving programs
are generally available: Windows2000/NT/98/95,SCO Unix, UnixWare7, SVR4.2,
Linux, IBM AIX etc. Notice that the driving programs provided should
correspond with real COM or tty ports, instead of random ports. This is called
RealCom, or RealTTY, or fixed terminal etc.
GPORT serial port equipment server can provide 2 types of fixed ports for
the clients to choose for different applications and to comprehensively support all
mainstream operation systems.
