Introduction
Manual Documentation Number: ESP901-902-3704 Chapter 1 3
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Communication Modes The ESP901 and ESP902 Serial Servers enable communication with
serial devices over a LAN or WAN. Serial devices no longer are
limited to a physical connection to the PC COM port. They can be
installed anywhere on the LAN using TCP/IP or UDP/IP
communications. This allows traditional Windows PC software access
to serial devices anywhere on the LAN/WAN network.
Direct IP Mode
Direct IP connections allow applications using TCP/IP or UDP/IP
socket programs to communicate with the asynchronous serial ports on
the Serial Server. In this type of application the Serial Server is
configured as a TCP or UDP server. The socket program running on the
PC establishes a communication connection with the Serial Server.
The data is sent directly to and from the serial port on the server. When
using UDP protocol the server can be configured to broadcast data to
and receive data from multiple IP addresses.
Virtual COM Mode
Install Virtual COM Mode allows the user to add a driver, to provide a
virtual COM port on the computer. The new COM port shows up in the
Device Manager. Windows programs using standard Windows API
calls are able to interface to virtual COM ports. When a program on the
PC opens the new COM port, it communicates with the remote serial
device connected to one of the ports on the Serial Server.
After connection, the LAN is transparent to the program and serial
device. Applications are able to work just as if the serial device is
connected directly to a physical COM port on the computer. The virtual
COM port software converts the application’s data into IP packets,
sends it across the network to the Serial Server, which converts the IP
packet back to serial data and sends the data out a serial port located on
the Serial Server.
To use this mode, the Serial Server must be set to either TCP/server or
UDP/server with a designated communication port number. The virtual
COM driver is the TCP or UDP client.
Introduction
4 Chapter 1 Manual Documentation Number: ESP901-902-3704
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 – www.bb-elec.com
B&B Electronics Ltd – Westlink Commercial Pk – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445 – www.bb-europe.com
Paired Mode
Paired Mode is also called serial tunneling. In this mode any two serial
devices that can communicate with a serial link will be able to
communicate using two Serial Servers and the LAN.
Two Serial Servers are connected to a network, one configured as a
TCP or UDP client and the other as a TCP/UDP server. When setting
up the server the remote IP address section must contain the address of
the client. This will allow the client’s IP address to pass the IP address-
filtering feature of the server. Conversely, the Remote IP address of the
client must contain the server’s IP address. Both communication port
numbers must be the same.
Heart Beat
The Heart Beat protocol connection provides a reliable
communications connection in Virtual COM Port Mode or with Paired
Connection Mode. This feature restores the connection if
communications are temporarily lost at either end due to loss of power
or Ethernet connection.
Without this feature a device that loses a connection and stops
communicating would not be able to reconnect without human
intervention. A TCP data connection can be lost when there is a power
failure or temporary loss of an Ethernet connection on either the client
or server. If a loss occurs the Heart Beat feature will try to reconnect
the TCP data connection every five seconds until communications is
established again. The Heart Beat feature is available for use in Virtual
COM Port Mode and Paired Connection Mode. This is not available
when using a UDP application.