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MSS User Guide 5: Using the MSS
5-10
Wiring Requirements
Serial signals work differently when the MSS is in modem mode. First, the MSS will
enable DTRWait and will not drive DTR until a valid connection is made with the ATDT
command (see Modem Mode Commands). Second, the MSS will drop DTR whenever
the TCP session is disconnected. DSRLogout is enabled implicitly. The intent is that the
MSS DTR signal will be used as a simulated CD signal to the attached serial device.
If you are using an MSS with a DB25 connector, you will need to change the way you
wire the DB25 adapters.
The serial device's DTR goes out to BOTH its own DSR in and the MSS DSR in. When
the device asserts its DTR, it will see its DSR asserted. That way the device thinks that
the "modem" (the MSS) is ready to accept commands all the time, and the MSS can log
out the serial port when the device disconnects.
The MSS DTR out goes to the serial device's CD in. That way the MSS can signal the
serial device that there is a valid connection, and the serial device will know it can send
data to the remote device.
Sequential Hostlist Mode
Although Multihost Mode allows up to 16 simultaneous connections, Sequential Hostlist
Mode uses the host table for failover connections.
Figure 5-19: Enabling Sequential Hostlist Mode
Local>> CHANGE PORT 1 DEDICATED SEQLIST
When Sequential Hostlist Mode is enabled, the MSS attempts to make a connection to
the first address in the hostlist. If it succeeds it communicates with that host only and
does not attempt to connect to any further addresses on the list. If it fails to connect to
the first address, it will attempt to connect to the next address on the list. Again, once it
successfully connects to an address on the list, it will not attempt further connections.
COM Port Redirector
The Lantronix COM Port Redirector application allows PCs to share modems and other
serial devices connected to an MSS using Microsoft Windows or DOS communication
applications. Using their existing communications software, PC users dial out to a remote
host through a modem connected to the MSS.
The Redirector intercepts communications to specified COM ports and sends them over
an IP (wired or wireless) network connection to the MSS serial port. This enables the PC
to use the MSS serial port as if it were one of the PC COM ports.
The COM Port Redirector software and installation instructions are included on the
distribution CD-ROM.