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Haxxio UDP Serial Port Redirector
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RS485 networks work differently to the common RS232 cable.
A RS232 cable connects just two devices.
A RS485 network has a number (generally limited to 32) of devices all connected to a 2 wire (almost always a single twisted pair) bus. All devices can listen on this bus, and one device may transmit at one time.
Generally, one device will be the "master", and it will poll all the other devices, the "slaves".
This type of network is relatively easy to replace with a UDP network based system. In particular, as the application is based on a poll-and-reponse paradigm, with all data neatly packaged into error checked packets, a network based solution can be deployed that is as reliable as the traditional twisted pair.
It is also possible to augment a RS485 network to either allow expansion to non-RS485 devices, or to allow a remote computer using IP to connect to the RS485 network.
The lowest cost terminal server with both an RS485 port and is UDP capable that we are aware of is the Moxa DE-211. The Moxa range shares similar software, so any of the Moxa range should work happily with the Redirector.
The Terminal Servers and Redirerector(s) can be configured either as as one-to-many application, as described in Groups of PCs and/or terminal Servers communicating , or as a genuine many-to-many.
To configure a many-to-many network, all terminal servers and redirectors should be configured to transmit to the broadcast address. That way, any data transmitted by one device will be "heard" by all. This is the traditional mode for RS485 networks, as there is no physical addressing, only devices that know what btheir own addresses is, and can thus respond when spoken to.