Senatek HELLODEVICE LITE SERIES LS100 Manuale Utente

 

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- Sync-Sent 

If the LS100 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. 

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]. 

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  LS100 works as a TCP server, and the default TCP state is [Listen] in  this  mode.  The  LS100 

supports only one TCP socket connection per one serial port. If a connection is currently established, 

the additional connection requests will be rejected. The remote host will be either Ethernet-Serial 

communication devices acting as a TCP client or a socket program acting as a TCP client running on 

users’ PC. 

 

1) Typical State Transition 

 

[Listen] --> [Sync-Received] --> [Established] --> [Data] --> [Closed] --> [Listen] 

 

At start-up, an initial TCP state is [Listen]. If there is any incoming TCP connection request, the state 

will be changed into [Sync-Received], then [Established], which means a session is opened. For a 

while, data will be transferred between the hosts. This is the [Data] state. The session will be 

disconnected due  to the request of one of them, which is [Closed] state. And then, the state is 

automatically changed to its original state, [Listen].