diff --git a/code/reference/ch_wireshark/TCPFlowControlDemo/Server.py b/code/reference/ch_wireshark/TCPFlowControlDemo/Server.py
new file mode 100644
index 0000000..fa8b96f
--- /dev/null
+++ b/code/reference/ch_wireshark/TCPFlowControlDemo/Server.py
@@ -0,0 +1,32 @@
+import socket
+import time
+
+def recv_data(sock,length):
+    data=b''
+    while len(data) < length:
+        more = sock.recv(length - len(data))
+        if not more:
+            pass
+            #raise EOFError('Cannot RECV execpting data')
+        data += more
+    return data         
+
+
+s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+# 设置接收缓冲区大小为1024
+s.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 1024)
+
+s.bind(('0.0.0.0', 9999))
+s.listen(1)
+print("Sever listening on 9999...")
+try:
+    sc, addr = s.accept()
+    while True:
+        rcvdata = recv_data(sc,16)
+        time.sleep(0.01)
+        pass
+
+finally:
+    sc.close()
+    s.close()
diff --git a/code/reference/ch_wireshark/TCPFlowControlDemo/client.py b/code/reference/ch_wireshark/TCPFlowControlDemo/client.py
new file mode 100644
index 0000000..de8f653
--- /dev/null
+++ b/code/reference/ch_wireshark/TCPFlowControlDemo/client.py
@@ -0,0 +1,24 @@
+import socket
+import time
+
+ip_port = ("server", 9999)
+data = "0123456789\n"*100
+
+c = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+try:
+    c.connect(ip_port)
+    print("Connected.")
+    time.sleep(1)  
+    i=0
+    while i<10:
+        print("Send:"+data)
+        c.send(data.encode())
+        i=i+1
+
+finally:
+    print("Sent. Waiting....")
+
+while True:
+    time.sleep(0.001)
+
diff --git a/figure/chapters/wireshark/TCP-structure.png b/figure/chapters/wireshark/TCP-structure.png
index cf32bf4..0bf5716 100644
Binary files a/figure/chapters/wireshark/TCP-structure.png and b/figure/chapters/wireshark/TCP-structure.png differ