Add a udp program and a ping test script

ping.py

@@ -0,0 +1,18 @@
+import socket
+import sys
+import time
+
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+addr = ('localhost', 26099)
+sock.bind(addr)
+
+
+print("pinging...", file=sys.stderr)
+while True:
+        buf, raddr = sock.recvfrom(4096)
+        print("receive: " + buf.decode("utf-8"))
+        buf = "this is a ping to port 6200!".encode('utf-8')
+        sock.sendto(buf, ("127.0.0.1", 6200))
+        buf = "this is a ping to reply!".encode('utf-8')
+        sock.sendto(buf, raddr)
+        time.sleep(1)