Lantronix MSS1-T, Reference Manual

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Emulating a Direct Serial Connection Using the MSS
5 - 8
5.3 Emulating a Direct Serial Connection
Two MSS serial servers can be connected to emulate a direct serial connection on a LAN. MSSs
connected in this way can pass data only. They will not be able to pass status signals (DSR, DTS,
CTS/RTS, etc.) or preserve timing between characters. The basic network configuration for this
virtual serial line is shown in Figure 5-14.
Figure 5-14: Back-to-back MSS Connection
Assuming the MSS serial port parameters have been configured properly, they would be
configured as follows:
mss_a
Local>> CHANGE DEDICATED TCP 192.168.5.10:3001T
Local>> CHANGE AUTOSTART ENABLED
mss_b
Local>> CHANGE ACCESS REMOTE
Local>> CHANGE DEDICATED NONE
Local>> CHANGE AUTOSTART DISABLED
NOTE: If the two MSSs are on different IP subnets, the default gateway on each unit will
have to be configured with the Change Gateway command (see page 6-10).
The above commands create a raw (8-bit clean) TCP connection between the serial ports of the two
MSSs once the units have been power-cycled. The commands for mss_a ensure that it will
automatically connect to mss_b each time it is booted. Similarly, the commands for mss_b ensure
that it is always available to accept connections from mss_a.
When the UDP protocol is used, there is no connection. Each MSS must be told explicitly which
hosts it is allowed to accept packets from. Broadcast or multicast IP addresses can be specified to
allow an MSS to send packets to all hosts on a subnet.
In UDP mode, each MSS would have to be configured to both send packets to and accept packets
from the other MSS. The configuration is as follows:
mss_a
Local>> CHANGE DEDICATED TCP 192.168.5.10:4096U
Local>> CHANGE AUTOSTART ENABLED
Local>> CHANGE ACCESS DYNAMIC
mss_b
Local>> CHANGE DEDICATED TCP 192.168.5.2:4096U
Local>> CHANGE AUTOSTART ENABLED
Local>> CHANGE ACCESS DYNAMIC
Setting up Dedicated hosts ensures that the units will always talk to each other. Enabling
Autostart for both units enables one MSS to send data to the other MSS without having to wait for
a serial carriage return to start the session. Finally, when Autostart is enabled, the access mode
must be either Local or Dynamic (more flexible).
NOTE: Autostart can be disabled if you want the MSS to wait for a carriage return before
sending data. Also, the Autostart character can be changed, if desired, using the
Change Autostart command.
Serial Device
Serial Device
mss_a mss_b
Ethernet
192.168.5.2 192.168.5.10