[En-Nut-Discussion] TCP

[Michael Baverso]

I apologize for the lengthy e-mail. This was the clearest way to ask my
question. I am working on a Modbus/TCP interface to a serial device using
the Ethernut. I have a test client on my PC that issues Modbus/TCP requests,
a connection is successfully established per segments 1-3 below, the query
is sent(segment 4) and the Ethernut responds with an (ACK)(segment 5). I
have tried using StreamI/O and NutTcpSend to respond to the query. It seems
that because my response was not included in the (ACK)(segment 5) that the
Modbus client begins to close the connection. Is there a way to send app
data with this first (ACK)(segment 5)?????
 No. Time        Source                Destination           Protocol Info
1 0.000000    192.168.2.15          192.168.2.50          TCP      1131 >
502 [SYN] Seq=1354601339 Ack=0
2 0.001214    192.168.2.50          192.168.2.15          TCP      502 >
1131 [SYN, ACK] Seq=1000000
3 0.001372    192.168.2.15          192.168.2.50          TCP      1131 >
502 [ACK] Seq=1354601340 Ack=1000001
4 0.001600    192.168.2.15          192.168.2.50          Modbus/TCP
query
5 0.003187    192.168.2.50          192.168.2.15          TCP      502 >
1131 [ACK] Seq=1000001 Ack=1354601352
6 0.995268    192.168.2.15          192.168.2.50          TCP      1131 >
502 [FIN, ACK] Seq=1354601352Ack=1000001
7 0.996529    192.168.2.50          192.168.2.15          TCP      502 >
1131 [ACK] Seq=1000001 Ack=1354601353       8 0.997425    192.168.2.50
192.168.2.15          TCP      502 > 1131 [FIN, ACK]
Seq=1000001Ack=1354601353
9 0.997529    192.168.2.15          192.168.2.50          TCP      1131 >
502 [ACK] Seq=1354601353 Ack=1000002

Regards,

Mike Baverso