Python socket not receiving anything
-
19-09-2019 - |
Question
I'm trying to receive a variable length stream from a camera with python, but get weird behaviour. This is Python 2.6.4 (r264:75706) on linux(Ubuntu 9.10)
The message is supposed to come with a static header followed by the size, and rest of the stream. here is the code
from socket import *
import array
import select
HOST = '169.254.0.10'
PORT = 10001
BUFSIZ = 1024
ADDR = (HOST, PORT)
tcpCliSock = socket(AF_INET, SOCK_STREAM)
tcpCliSock.connect(ADDR)
tcpCliSock.setblocking(0)
def dump(x):
dfile = open('dump','w')
dfile.write(x)
dfile.close
data='I'
tcpCliSock.send(data)
tcpCliSock.shutdown(1)
ready_to_read, ready_to_write, in_error = select.select(
[tcpCliSock],
[],
[],
30)
if ready_to_read == []:
print "sokadens"
data=''
while len(data)<10:
chunk = tcpCliSock.recv(1024)
print 'recv\'d %d bites'%len(data)
data=data+chunk
index=data.find('##IMJ')
if index == -1:
dump(data)
raise RuntimeError, "imahe get error"
datarr = array.array('B',data)
size=datarr[6]+datarr[7]<<8+datarr[8]<<16+datarr[9]<<24
ready_to_read, ready_to_write, in_error = select.select(
[tcpCliSock],
[],
[],
30)
if ready_to_read == []:
print "sokadens"
while len(data)<size:
chunk = tcpCliSock.recv(1024)
data=data+chunk
outfile=open('resim.jpg','w')
outfile.write(data[10:])
outfile.close
tcpCliSock.close()
with this code I either get stuck in a "recv\'d 0 bites" loop(which happens rarely) or this:
`recv'd 0 bites`
Traceback (most recent call last):
File "client.py", line 44, in <module>
raise RuntimeError, "imahe get error"
RuntimeError: imahe get error
which is totally weird(receive 0 bytes but get out of the loop). The dumped data is erroneous, which is expected in that situation
Edit 1: the device is supposed to send a JPEG image, preceded by a 10-byte header. When(if) I get past the first loop, I need to check this header for correctness and size info. The program terminates with wrong data error, and the dump file is a bunch of binary garbage, so I have no Idea what I received at the end. I am pretty sure the device at the other side is trying to send the correct data.
Solution 2
Problem is resolved, interestingly shutdown(1) was causing the problem, the other side does not like http style shutdowns. There are also obvious typos and missing checks but they are not the problem.
OTHER TIPS
You don't really know how many bytes you received, since your code is:
data=''
while len(data)<10:
chunk = tcpCliSock.recv(1024)
print 'recv\'d %d bites'%len(data)
data=data+chunk
i.e., you're receiving bytes in chunk
, but what you're printing is len(data)
before you update data
. So of course it will print 0 the first time, always -- then it will update data
and exit if the chunk
was at least 10 bytes.
This info is not sufficient to debug your problem, but printing len(chunk), and len(data) upon exiting the loop, can't hurt the attempt to understand what's going on. Also, what's in dump
when you exit with the imahe get error
message?