Why python asyncio coroutine is pausing at the line socket.recv(1024) ? why the while loops are failed to cross yeild statements? - asynchronous

Question

I have a small application where, one coroutine will send data and the other coroutine will receive data and logs whether it received the exact transmitted data or not.
Both coroutines are in while loops. Some how, the trans() coroutine and recv() coroutine are not proceeding ahead when they hit the line yield from XXXXXXX
data, server = yield from recv_sock.recvfrom(1024)
Here is the code
import asyncio
import socket
import time
import datetime
import logging
trans_addr = ('localhost', 5555)
recv_addr = ('localhost',6666)
#asyncio.coroutine
def trans():
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(trans_addr)
i = 0
global sen_data
while True:
print("hi")
sen_data = "HELLO " + str(i)
sent = yield from sock.sendto(sen_data.encode(), recv_addr)
print(sent)
print("hi1")
yield from time.sleep(2)
i += 1
print("hi1")
#asyncio.coroutine
def recv():
recv_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
recv_sock.bind(recv_addr) # binding the receiving end to 1.241 and port 6666
#recv_sock.setblocking(0)
while True:
try:
print("hello")
data, server = yield from recv_sock.recvfrom(1024)
print("hello2")
if (data):
recv_data = data.decode()
if (sen_data == recv_data):
logging.info("transmitted data :" + sen_data + " is Received as :" + recv_data + " at :" + str(
datetime.datetime.now()) + '\n')
print("transmitted data :" + sen_data + " is Received as :" + recv_data + " at :" + str(
datetime.datetime.now()) + " from :" + str(server) + '\n')
else:
logging.critical("Data missed : ")
logging.critical("Transmitted data " + sen_data + " is != " + "received data : " + recv_data + '\n')
print("data is missing--->")
print("Transmitted data " + sen_data + " is != " + "received data : " + recv_data + '\n')
except:
pass
# print("not receiving data due to some fault in the receiving socket")
# time.sleep(1)
loop=asyncio.get_event_loop()
tasks = [loop.create_task(trans()), loop.create_task(recv())]
wait_tasks = asyncio.wait(tasks)
loop.run_forever()
loop.run_until_complete(wait_tasks)
Output is:
hello
hi
Can anyone let me know,why the coroutines are failed to cross the yield from commands? i am using python 3.3.2

Answer 1

yield from or await should be used with coroutines. recvfrom is not a coroutine. For example, you can use loop.sock_recv() instead:
reader, writer = socket.socketpair()
writer.setblocking(False)
reader.setblocking(False)
await loop.sock_recv(...)
await loop.sock_sendall(...)