SENA Rhio10 - Manual (Page 24)

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For easier understanding of TCP modes, a simplified State Transition Diagram is often used.
And too help users understand the diagram, the TCP state of the Rhio10 is briefly described as
follows.
Listen
It represents “a waiting for a connection request from any remote host”. It is a default start-up
mode when it is set as TCP server mode. This state is valid only in TCP server mode operation.
Closed
It means “No connection state at all”. If the data transfer is completed, the state is changed to
this state if one of the host requests disconnection request. If it is in TCP server mode, the state
is automatically changed to [Listen] mode. It is a default start-up mode when it is set as TCP
client mode or TCP server/client mode.
Sync-Received
In TCP server mode, the state will be changed from [Listen] to [Sync-Received], if any remote
host sends connection request. If the Rhio10 accepts the request, the state will be changed into
[Established]. This state is not valid in TCP client mode.
Sync-Sent
If the Rhio10 sends 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. This
state is valid only in TCP client mode.
Established
It represents “an open connection”. If one of the hosts accepts a connection request from the
other host, 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.