SENA STS Series - Manual (Page 44)

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1) Typical State Transition
[Listen] --> [Sync-Received] --> [Established] --> [Data] --> [Closed] --> [Listen]
Or
[Listen] --> [Sync-Sent] --> [Established] --> [Data] --> [Closed] --> [Listen]
The initial state is [Listen]. If there are data coming from the serial port, it will connect to the remote
host as a TCP client and then transfer data through the TCP port. If there is incoming connection
request from the remote host, it will accept the connection as a TCP server, and then transfer data
through the serial port. Thus, users can assume that the STS Series is always connected to the
specified remote host.
2) Operations
 Serial data transfer
Whenever the serial device sends data through the serial port of the STS Series, data will be
accumulated on the serial port buffer of the STS Series. If the buffer is full or the time gap reaches the
inter-character timeout (See Options in section 4.2.9. Serial Port Parameters for details on inter-
character timeout), the STS Series connect to the registered remote host(s). If a TCP session has not
been established yet and the STS Series succeeds in connecting to the remote host, the data in the
serial port buffer will be transferred to the host. Otherwise, all the data stored in the buffer will be
cleared.
 Session disconnection
The connected session will be disconnected when the remote host sends disconnection request or
when no data transfer activity is found through the serial port for certain amount of time, which is
“Inactivity timeout”. All the data remained in the serial port buffer will be cleared when it is
disconnected.
 Connection request from remote host
All the incoming TCP connection requests will be rejected in TCP client mode.
3) Parameters
 TCP listening port
This is the TCP port number through which remote host can connect a TCP session, and, send and
receive data. Incoming connection request to the ports other than TCP Listening Port will be rejected.
The STS Series does restrict the port number from 1024 to 65535 and if it is set as 0 only outgoing
connection is permitted. (TCP server mode)