ACK packets forged issues: "This frame is a (suspected) retransmission" - python-3.x

Question

I'm playing with scapy. I'm trying to forge JUST PSH/ACK and ACK packets in sequence
I coded two tools: A which sends PSH/ACK packets and then sniffs the resulting ACK, writing the sequence in a file to use it later
.....
bitack = random.randrange(1,656787969)
bitseq = random.randrange(1,4294967295)
if os.path.exists('test.txt'):
with open('test.txt','r') as f:
bitseq = int(f.read())
else:
with open('test.txt','w') as f:
f.write(str(bitseq))
.....
text = "Ok"
TSval = int(time.time())
TSecr = TSval
acker = IP(src="127.0.0.1",dst=destinazione"127.0.0.1")/TCP(sport=88,dport=8888,
flags="PA", seq=bitseq, ack=bitack, options=[('Timestamp', (TSval, TSecr))])/text
send(acker)
.....
rx = sniff(filter="host 127.0.0.1 and src port 8888", iface="lo", count=1)
seqcc = rx[0].getlayer(TCP).seq
ackcc = rx[0].getlayer(TCP).ack
with open('test.txt','w') as f:
f.write(str(ackcc))
print("SEQFINALE=", ackcc)
B: which sends ACK packets AFTER it sniffs a PSH/ACK packet from A. I know the ack packets contain text ( in this example the same of A), but this is what I want
....
rx = sniff(filter="host 127.0.0.1 and dst port 8888", iface="lo", count=1)
seqcc = rx[0].getlayer(TCP).seq
print("seq:", seqcc)
ackcc = rx[0].getlayer(TCP).ack
print("ack:", ackcc)
var = rx[0][Raw].load.decode(encoding='utf-8', errors='ignore')
acker = IP(src="127.0.0.1",dst="127.0.0.1")/TCP(sport=8888,dport=88, flags="A",
seq=ackcc, ack=seqcc + int(len(var)), options=[('Timestamp', (TSval, TSecr))])/var
send(acker)
.....
Everything works fine expect that wireshark gives some warning and I don't understand why:
"Expert Info (Note/Sequence): This frame is a (suspected) retransmission"
The first two packets are perfect:
Is there any issue in how I handle the sequence number/ ack number?
This makes me crazy

Answer 1

It is a retransmission. Your capture shows a frame from 8888 to 88 at seq=1 with 52 bytes of data (len=52). If you ever send another frame from 8888 to 88 at seq=1, it's a retransmission. TCP streams are in a single direction: A sends to B, B ACK's what A sent. (in this case, there should be an ACK=53 in a frame from 88 to 8888, either alone or piggybacking data.)