“Keep alive“ settings
A TCP/IP connection remains open after being established until one of the communicating devices closes
the connection. If the physical connection between the WI-Client and the other device is interrupted without
closing the TCP/IP connection, there is a possibility that the WI-Client is not able to reconnect. The TCP/IP
socket can be programmed to send an empty data package to the communication partner in regular intervals
(keep alive period). If the communication partner supports this mode, it sends a corresponding answer. This
answer is proof that the connection is still intact. If there is no answer for a number of times (keep alive
probes), the TCP/IP connection is closed and the WI-Client starts the TCP/IP socket again.
“Send trigger” configuration
The data received by the WI-Client are first temporarily stored. There are different criteria when the stored
data will be sent over the LAN/WLAN.
1)
Byte trigger
: The user defines a number of Bytes. After reaching that number, the stored data are
sent.
2)
Timeout
: After receiving a character a timer with the programmed value is started. Each received
character restarts the timer. Once the timer has elapsed the stored data are sent.
3)
Delimiter
: The user defines a certain character. When this character is received, the stored data are
sent.
The parameter “
receive fifo size”
defines the quantity of bytes that can be stored in a ringbuffer before the
data is sent to the (W)LAN interface. If you use the WI-Client in an application that receives permanently
data via the serial interface the “receive fifo size” has to be set to a value between 1024 and 2048 bytes.
Because the WI-Client needs all the available RAM memory in a situation of authentication with 802.1x
(PEAP,TLS) this value is set to a value of 256 Bytes by default to save memory space.
Handshake mode
This defines how the communication partners are signaling their ability to send and receive data. With the
status lines RTS and DTR the WI-Client reports that it is ready to receive. The status lines CTS and DTR are
inputs where the communication partner reports its readiness to receive. The signals DCD and RI can be
forwarded to the WI-Clients LAN/WLAN communication partner.
The WI-Client be controlled remote or local to handle the data flow.
The following modes are available to the user:
1)
no handshake
: The CTS/DSR signals are not utilized. CTS/RTS are set to active when the serial
interface is connected over the LAN/WLAN.
2)
XON / XOFF
: The WI-Client sends and receives the control characters XON = 0x11 and XOFF =
0x13. The WI-Client sends a XOFF to his serial communication partner when the memory buffer is
almost full and a XON when it is almost empty.
3)
RTS/CTS
: The WI-Client signals that it is ready to receive over the RTS line and recognizes the CTS
signal to determine if its serial partner is ready to receive.
4)
DTR/DSR
: The WI-Client signals that it is ready to receive over the DTR line and recognizes the
DSR signal to determine if its serial partner is ready to receive.
5)
Remote
: In this mode the WI-Client transmits the state of the status lines CTS, DSR, RI and DCD to
its LAN/WLAN communication partner. This happens over a different socket (port). This makes it
necessary for the user to enter more specifications.
The state of the status lines are described by strings of letters.
A capital letter means the signal is active, a small letter means inactive.
’D’ = DSR active
‘d’ = DSR inactive
’R’ = CTS active
‘r’ = CTS inactive
’C’ = DCD active
‘c’ = DCD inactive
’I’ = DSR active
‘i’ = DSR inactive
The WI-Client interprets the received data as follows:
’D’ -> set DTR to active
‘d’ = set DTR to inactive
’R’ -> set RTS to active
‘r’ = set RTS to inactive
‘C’ or ‘c’ and ‘I’ or ‘i’ are ignored.
WI-Client Manual Version 2.16 V3
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