Possibly related questions that seem close but don't describe my issue as I understand it:
- Reading all the data from a UDP socket
- Python UDP socket semi-randomly failing to receive
- Python raw socket listening for UDP packets; only half of the packets received
problem
Long file sent line by line doesn't go all the way through UDP over loopback.
long story
I have a long file consisting of lines and breaks that is identical to what I will get from another program over UDP locally. Let me emphasize that the program sending the packets will do so over UDP (there is no choice here), and cannot be feasibly modified to process ACK requests etc. while sending.
It looks like this (this is the tail):
StimulusTime 56398
Signal(0,2) -79.5457
Signal(0,4) -81.7426
Signal(0,6) -83.9978
Signal(0,9) -63.3755
Signal(0,11) -15.6045
Signal(0,13) 31.1299
Signal(0,16) 75.7539
Signal(0,18) 98.301
Signal(0,20) 98.301
Signal(0,22) 48.4546
Signal(0,25) 3.73159
Signal(0,27) -49.9798
Signal(0,29) -77.8449
Signal(1,0) -22.0332
Signal(1,2) -60.6384
Signal(1,4) -98.0858
Signal(1,6) -86.4579
Signal(1,9) -68.9173
Signal(1,11) -31.5552
Signal(1,13) 35.2906
Signal(1,16) 77.0686
Signal(1,18) 96.3836
Signal(1,20) 95.7246
Signal(1,23) 25.6074
Signal(1,25) -20.2101
Signal(1,27) -60.2933
Signal(1,29) -83.8169
Signal(2,0) -31.8826
Signal(2,2) -53.5045
Signal(2,4) -89.9895
Signal(2,7) -84.4503
Signal(2,9) -59.7016
Signal(2,11) -12.8569
Signal(2,13) 28.857
Signal(2,15) 58.0577
Signal(2,18) 96.4222
Signal(2,20) 79.783
Signal(2,22) 58.6463
Signal(2,25) -3.24883
Signal(2,27) -45.5
Signal(2,29) -88.8937
Signal(3,0) -18.6625
Signal(3,2) -53.3978
Signal(1,16) 58.784
Signal(1,17) 44.7782
Signal(1,18) 6.247
Signal(1,19) -12.0855
Signal(1,20) -33.7644
Signal(1,21) -49.4406
Signal(1,22) -67.5791
Signal(1,23) -92.0336
Signal(1,24) -93.9841
END
I wrote code that takes this file and sends it a line at a time over UDP locally, and then code that receives it and parses it based on the data type.
Sender:
import socket
import sys
# Sends udp test data piped in from STDIN to the listener.
# ex: cat sampleoutput.txt | python testsender.py
UDP_IP = "127.0.0.1"
UDP_PORT = 5000
print "UDP target IP:", UDP_IP
print "UDP target port:", UDP_PORT
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
# Send from stdin
if len(sys.argv) < 2:
while True:
line = sys.stdin.readline()
if line:
sock.sendto(line, (UDP_IP, UDP_PORT))
else:
break
# get from file arg
else:
myfile = open(str(sys.argv[1]), "r")
while True:
line = myfile.readline()
if line:
sock.sendto(line, (UDP_IP, UDP_PORT))
else:
break
sock.close()
Listener:
import socket
from array import array
UDP_IP = "127.0.0.1"
UDP_PORT = 5000
sock = socket.socket(socket.AF_INET, # Internet
socket.SOCK_DGRAM) # UDP
sock.bind((UDP_IP, UDP_PORT))
while True:
data, addr = sock.recvfrom(1024) # buffer size arg
print data
# write to file for later testing
# file = open("testdummy.txt", "a")
# file.write(data)
if data == "END\n":
break
I was able to use the above listener to produce the test file from the original program, so it should work. Unfortunately, it fails around 500 lines of payload, as tested by tail -n 500 testdummy.txt | python testsender.py, although it's somewhat random. Specifically, the listener does not receive all of the sent lines before the sender exits, leaving it hanging, waiting for the "END\n" string.
As I understand it, the socket is already in blocking mode--how can I prevent this from occurring?
