SENA LS110 - Manual (Page 26)

26
For easier understanding of TCP modes, a simplified State Transition Diagram is often used. And to
help users understand the diagram, the TCP state of the LS110 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 LS110 accepts the request, the state will be changed into
[Established]. This state is not valid in TCP client mode.
 Sync-Sent
If the LS110 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.