SENA PS400 - Manual (Page 29)

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4.1 Host mode configuration
4.1.1 Overview
Host mode represents the operating session mode of the HelloDevice Pro Series. Several host modes
are available for the data communication between serial devices and remote hosts. Since TCP is
connection-oriented protocol, server, client, server/client modes are provided. Other than those TCP
based modes, UDP mode is provided for connectionless communication. Modem emulation mode
supports several basic AT commands for TCP session control so that users can change the host mode
on-line from the serial device by using AT commands. Table 4-2 shows the brief description of the host
modes.
Table 4-2. The HelloDevice Pro Series TCP/IP session modes
Mode Description
TCP server Select this mode, when users want the HelloDevice Pro Series to operate as a TCP server.
The HelloDevice Pro Series stands by until there is any TCP connection request. If TCP
connection is not already established at that time, the HelloDevice Pro Series accepts the
request and the session is established. In the established state, it transmits the data through
the corresponding serial port if there is any data from the remote host. Since the HelloDevice
Pro Series supports only one TCP session per serial port, the additional TCP connection
request will be rejected if already established
. This mode is useful when users want to send
data to the serial device at any time they want.
TCP client Select this mode, when users want the HelloDevice Pro Series to operate as a TCP client.
When the serial device sends data or pre-defined timer is expired, the HelloDevice Pro Series
tries to establish a TCP connection to a remote server through its TCP port. If a TCP session is
established between them, the HelloDevice Pro Series will send data to the server. If there’s
any data from the server during the session, it will also send the data through the serial port.
However, if the HelloDevice Pro Series failed to connect to the remote server, the data from
the serial port will be discarded. This is useful when the serial device initiates sending data
such as data gathering application.
TCP
server/client If you are not sure which mode to choose, select this mode since it will be applied in most
applications. In this mode, the HelloDevice Pro Series operates as TCP server AND client. If
the connection is not established, it will accept all incoming connection and connect to the
remote host if there are any data from the serial device. Otherwise, it will send data back and
forth. In summary, the HelloDevice Pro Series will work as if it is virtually connected to the
remote host.
UDP
tunneling The UDP tunneling mode operation is similar to that of TCP server/client mode except that it is
based on UDP protocol and only one pre-defined remote host is able to communicate with the
HelloDevice Pro Series.
UDP server While UDP tunneling mode allows only one remote host for UDP communications, UDP server
mode allows any remote host to access the HelloDevice Pro Series. In this mode, the
HelloDevice Pro Series gets the information on the remote host from the latest incoming
datagram information.
Modem
emulation Select this mode when the serial device already supports modem AT commands or users
want to perform the session control by using AT commands. Only TCP session is supported.