[python] Python handling socket.error: [Errno 104] Connection reset by peer

When using Python 2.7 with urllib2 to retrieve data from an API, I get the error [Errno 104] Connection reset by peer. Whats causing the error, and how should the error be handled so that the script does not crash?

ticker.py

def urlopen(url):
    response = None
    request = urllib2.Request(url=url)
    try:
        response = urllib2.urlopen(request).read()
    except urllib2.HTTPError as err:
        print "HTTPError: {} ({})".format(url, err.code)
    except urllib2.URLError as err:
        print "URLError: {} ({})".format(url, err.reason)
    except httplib.BadStatusLine as err:
        print "BadStatusLine: {}".format(url)
    return response

def get_rate(from_currency="EUR", to_currency="USD"):
    url = "https://finance.yahoo.com/d/quotes.csv?f=sl1&s=%s%s=X" % (
        from_currency, to_currency)
    data = urlopen(url)
    if "%s%s" % (from_currency, to_currency) in data:
        return float(data.strip().split(",")[1])
    return None


counter = 0
while True:

    counter = counter + 1
    if counter==0 or counter%10:
        rateEurUsd = float(get_rate('EUR', 'USD'))

    # does more stuff here

Traceback

Traceback (most recent call last):
  File "/var/www/testApp/python/ticker.py", line 71, in <module>
    rateEurUsd = float(get_rate('EUR', 'USD'))
  File "/var/www/testApp/python/ticker.py", line 29, in get_exchange_rate
    data = urlopen(url)
  File "/var/www/testApp/python/ticker.py", line 16, in urlopen
    response = urllib2.urlopen(request).read()
  File "/usr/lib/python2.7/urllib2.py", line 126, in urlopen
    return _opener.open(url, data, timeout)
  File "/usr/lib/python2.7/urllib2.py", line 406, in open
    response = meth(req, response)
  File "/usr/lib/python2.7/urllib2.py", line 519, in http_response
    'http', request, response, code, msg, hdrs)
  File "/usr/lib/python2.7/urllib2.py", line 438, in error
    result = self._call_chain(*args)
  File "/usr/lib/python2.7/urllib2.py", line 378, in _call_chain
    result = func(*args)
  File "/usr/lib/python2.7/urllib2.py", line 625, in http_error_302
    return self.parent.open(new, timeout=req.timeout)
  File "/usr/lib/python2.7/urllib2.py", line 406, in open
    response = meth(req, response)
  File "/usr/lib/python2.7/urllib2.py", line 519, in http_response
    'http', request, response, code, msg, hdrs)
  File "/usr/lib/python2.7/urllib2.py", line 438, in error
    result = self._call_chain(*args)
  File "/usr/lib/python2.7/urllib2.py", line 378, in _call_chain
    result = func(*args)
  File "/usr/lib/python2.7/urllib2.py", line 625, in http_error_302
    return self.parent.open(new, timeout=req.timeout)
  File "/usr/lib/python2.7/urllib2.py", line 400, in open
    response = self._open(req, data)
  File "/usr/lib/python2.7/urllib2.py", line 418, in _open
    '_open', req)
  File "/usr/lib/python2.7/urllib2.py", line 378, in _call_chain
    result = func(*args)
  File "/usr/lib/python2.7/urllib2.py", line 1207, in http_open
    return self.do_open(httplib.HTTPConnection, req)
  File "/usr/lib/python2.7/urllib2.py", line 1180, in do_open
    r = h.getresponse(buffering=True)
  File "/usr/lib/python2.7/httplib.py", line 1030, in getresponse
    response.begin()
  File "/usr/lib/python2.7/httplib.py", line 407, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python2.7/httplib.py", line 365, in _read_status
    line = self.fp.readline()
  File "/usr/lib/python2.7/socket.py", line 447, in readline
    data = self._sock.recv(self._rbufsize)
socket.error: [Errno 104] Connection reset by peer
error: Forever detected script exited with code: 1

"Connection reset by peer" is the TCP/IP equivalent of slamming the phone back on the hook. It's more polite than merely not replying, leaving one hanging. But it's not the FIN-ACK expected of the truly polite TCP/IP converseur. (From other SO answer)

So you can't do anything about it, it is the issue of the server.

But you could use try .. except block to handle that exception:

from socket import error as SocketError
import errno

try:
    response = urllib2.urlopen(request).read()
except SocketError as e:
    if e.errno != errno.ECONNRESET:
        raise # Not error we are looking for
    pass # Handle error here.

There is a way to catch the error directly in the except clause with ConnectionResetError, better to isolate the right error. This example also catches the timeout.

from urllib.request import urlopen 
from socket import timeout

url = "http://......"
try: 
    string = urlopen(url, timeout=5).read()
except ConnectionResetError:
    print("==> ConnectionResetError")
    pass
except timeout: 
    print("==> Timeout")
    pass

You can try to add some time.sleep calls to your code.

It seems like the server side limits the amount of requests per timeunit (hour, day, second) as a security issue. You need to guess how many (maybe using another script with a counter?) and adjust your script to not surpass this limit.

In order to avoid your code from crashing, try to catch this error with try .. except around the urllib2 calls.