import socket
import traceback
import time

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setblocking(0)
# use a non-exist host/port, or a high delay remote port here as target
r = sock.connect_ex(('1.2.3.4', 12345))
print r
try:
    sock.send('abc')
except socket.error:
    traceback.print_exc(10)
    print 'in asyncore main loop, this exception is caught and handle_error() is called'

# for a non-exist target port, use long sleep time(1000 for example) to see the tcp syn retransfer in tcpdump/wireshark
# for a high delay target port, shorter sleep may be used(say, 10 seconds), and the second .send call() will be successful
time.sleep(10)
sock.send('abc')

time.sleep(15)
sock.close()