SENA PS810 - Manual (Page 44)

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It represents “a waiting for a connection request from any registered remote host”. It is a default start-
up mode when it is set as TCP mode.
[Closed]
It means “no connection state”. If the data transfer between a remote host and the Pro Series is
completed, the state is changed to this state as a result that either of the remote host or the Pro Series
sent a disconnection request. After this, the state is automatically changed to [Listen] mode.
[Sync-Received]
The state is changed from [Listen] to [Sync-Received] if one of the remote hosts has sent a connection
request. If the Pro Series accepts the request, the state is changed into [Established].
[Sync-Sent]
If the Pro Series has sent a connection request to a remote host, the state is changed from [Closed] to
[Sync-Sent]. This state is maintained until the remote host accepts the connection request.
[Established]
It represents “an open connection”. If one of the hosts, the remote host or the Pro Series, accepts a
connection request from the other, the connection is opened and state is changed into [Established].
[Data]
When it is in [Established] state, data from a host will be transferred to the other one. For easier
understanding of the TCP session operation, we called the state as [Data] state when actual data
transfer is performed. Actually, the [Data] mode is a part of [Established] state as is described in the
RFC 793 [Transmission Control Protocol]. This is a normal state for the data transfer phase of the
connection.
The Pro Series works as either TCP server or client according to the situation. This will be the typical
mode for most applications, since it will transfer the data either from serial port or from TCP port. The
default TCP state is [Listen] which is the same as that of TCP server mode.
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 Pro Series is always connected to the
specified remote host.