Overview
I have a simple question with code below. Hopefully I didn't make a mistake in the code.
I'm a network engineer, and I need to test certain linux behavior of our business application keepalives during network outages (I'm going to insert some iptables stuff later to jack with the connection - first I want to make sure I got the client & server right).
As part of a network failure test I'm conducting, I wrote a non-blocking Python TCP client and server that are supposed to blindly send messages to each other in a loop. To understand what's happening I am using loop counters.
The server's loop should be relatively straightforward. I loop through every fd that select says is ready. I never even import sleep anywhere in my server's code. From this perspective, I don't expect the server's code to pause while it loops over the client's socket , but for some reason the server code pauses intermittently (more detail, below).
I initially didn't put a sleep in the client's loop. Without a sleep on the client side, the server and client seem to be as efficient as I want. However, when I put a time.sleep(1) statement after the client does an fd.send() to the server, the TCP server code intermittently pauses while the client is sleeping.
My questions:
Should I be able to write a single-threaded Python TCP server that doesn't pause when the client hits time.sleep() in the client's fd.send() loop? If so, what am I doing wrong? <- ANSWERED
If I wrote this test code correctly and the server shouldn't pause, why is the TCP server intermittently pausing while it polls the client's connection for data?
Reproducing the scenario
I'm running this on two RHEL6 linux machines. To reproduce the issue...
Open two different terminals.
Save the client and server scripts in different files
Change the shebang path to your local python (I'm using Python 2.7.15)
Change the SERVER_HOSTNAME and SERVER_DOMAIN in the client's code to be the hostname and domain of the server you're running this on
Start the server first, then start the client.
After the client connects, you'll see messages as shown in EXHIBIT 1 scrolling quickly in the server's terminal. After a few seconds The scrolling pauses intermittently when the client hits time.sleep(). I don't expect to see those pauses, but maybe I've misunderstood something.
EXHIBIT 1
---
LOOP_COUNT 0
---
LOOP_COUNT 1
---
LOOP_COUNT 2
---
LOOP_COUNT 3
CLIENTMSG: 'client->server 0'
---
LOOP_COUNT 4
---
LOOP_COUNT 5
---
LOOP_COUNT 6
---
LOOP_COUNT 7
---
LOOP_COUNT 8
---
LOOP_COUNT 9
---
LOOP_COUNT 10
---
LOOP_COUNT 11
---
Summary resolution
If I wrote this test code correctly and the server shouldn't pause, why is the TCP server intermittently pausing while it polls the client's connection for data?
Answering my own question. My blocking problem was caused by calling select() with a non-zero timeout.
When I changed select() to use a zero-second timeout, I got expected results.
Final non-blocking code (incorporating suggestions in answers):
tcp_server.py
#!/usr/bin/python -u
from socket import AF_INET, SOCK_STREAM, SO_REUSEADDR, SOL_SOCKET
from socket import MSG_DONTWAIT
#from socket import MSG_OOB <--- for send()
from socket import socket
import socket as socket_module
import select
import errno
import fcntl
import time
import sys
import os
def get_errno_info(e, op='', debugmsg=False):
"""Return verbose information from errno errors, such as errors returned by python socket()"""
VALID_OP = set(['accept', 'connect', 'send', 'recv', 'read', 'write'])
assert op.lower() in VALID_OP, "op must be: {0}".format(
','.join(sorted(VALID_OP)))
## ref: man 3 errno (in linux)... other systems may be man 2 intro
## also see https://docs.python.org/2/library/errno.html
try:
retval_int = int(e.args[0]) # Example: 32
retval_str = os.strerror(e.args[0]) # Example: 'Broken pipe'
retval_code = errno.errorcode.get(retval_int, 'MODULEFAIL') # Ex: EPIPE
except:
## I don't expect to get here unless something broke in python errno...
retval_int = -1
retval_str = '__somethingswrong__'
retval_code = 'BADFAIL'
if debugmsg:
print "DEBUG: Can't {0}() on socket (errno:{1}, code:{2} / {3})".format(
op, retval_int, retval_code, retval_str)
return retval_int, retval_str, retval_code
host = ''
port = 6667 # IRC service
DEBUG = True
serv_sock = socket(AF_INET, SOCK_STREAM)
serv_sock.setsockopt(SOL_SOCKET, SOCK_STREAM, 1)
serv_sock.bind((host, port))
serv_sock.listen(5)
#fcntl.fcntl(serv_sock, fcntl.F_SETFL, os.O_NONBLOCK) # Make the socket non-blocking
serv_sock.setblocking(False)
sock_list = [serv_sock]
from_client_str = '__DEFAULT__'
to_client_idx = 0
loop_count = 0
need_send_select = False
while True:
if need_send_select:
# Only do this after send() EAGAIN or EWOULDBLOCK...
send_sock_list = sock_list
else:
send_sock_list = []
#print "---"
#print "LOOP_COUNT", loop_count
recv_ready_list, send_ready_list, exception_ready = select.select(
sock_list, send_sock_list, [], 0.0) # Last float is the select() timeout...
## Read all sockets which are output-ready... might be client or server...
for sock_fd in recv_ready_list:
# accept() if we're reading on the server socket...
if sock_fd is serv_sock:
try:
clientsock, clientaddr = sock_fd.accept()
except socket_module.error, e:
errstr, errint, errcode = get_errno_info(e, op='accept',
debugmsg=DEBUG)
assert sock_fd.gettimeout()==0.0, "client socket should be in non-blocking mode"
sock_list.append(clientsock)
# read input from the client socket...
else:
try:
from_client_str = sock_fd.recv(1024, MSG_DONTWAIT)
if from_client_str=='':
# Client closed the socket...
print "CLIENT CLOSED SOCKET"
sock_list.remove(sock_fd)
except socket_module.error, e:
errstr, errint, errcode = get_errno_info(e, op='recv',
debugmsg=DEBUG)
if errcode=='EAGAIN' or errcode=='EWOULDBLOCK':
# socket unavailable to read()
continue
elif errcode=='ECONNRESET' or errcode=='EPIPE':
# Client closed the socket...
sock_list.remove(sock_fd)
else:
print "UNHANDLED SOCKET ERROR", errcode, errint, errstr
sys.exit(1)
print "from_client_str: '{0}'".format(from_client_str)
## Adding dynamic_list, per input from EJP, below...
if need_send_select is False:
dynamic_list = sock_list
else:
dynamic_list = send_ready_list
## NOTE: socket code shouldn't walk this list unless a write is pending...
## broadast the same message to all clients...
for sock_fd in dynamic_list:
## Ignore server's listening socket...
if sock_fd is serv_sock:
## Only send() to accept()ed sockets...
continue
try:
to_client_str = "server->client: {0}\n".format(to_client_idx)
send_retval = sock_fd.send(to_client_str, MSG_DONTWAIT)
## send() returns the number of bytes written, on success
## disabling assert check on sent bytes while using MSG_DONTWAIT
#assert send_retval==len(to_client_str)
to_client_idx += 1
need_send_select = False
except socket_module.error, e:
errstr, errint, errcode = get_errno_info(e, op='send',
debugmsg=DEBUG)
if errcode=='EAGAIN' or errcode=='EWOULDBLOCK':
need_send_select = True
continue
elif errcode=='ECONNRESET' or errcode=='EPIPE':
# Client closed the socket...
sock_list.remove(sock_fd)
else:
print "FATAL UNHANDLED SOCKET ERROR", errcode, errint, errstr
sys.exit(1)
loop_count += 1
tcp_client.py
#!/usr/bin/python -u
from socket import AF_INET, SOCK_STREAM
from socket import MSG_DONTWAIT # non-blocking send/recv; see man 2 recv
from socket import gethostname, socket
import socket as socket_module
import select
import fcntl
import errno
import time
import sys
import os
## NOTE: Using this script to simulate a scheduler
SERVER_HOSTNAME = 'myServerHostname'
SERVER_DOMAIN = 'mydomain.local'
PORT = 6667
DEBUG = True
def get_errno_info(e, op='', debugmsg=False):
"""Return verbose information from errno errors, such as errors returned by python socket()"""
VALID_OP = set(['accept', 'connect', 'send', 'recv', 'read', 'write'])
assert op.lower() in VALID_OP, "op must be: {0}".format(
','.join(sorted(VALID_OP)))
## ref: man 3 errno (in linux)... other systems may be man 2 intro
## also see https://docs.python.org/2/library/errno.html
try:
retval_int = int(e.args[0]) # Example: 32
retval_str = os.strerror(e.args[0]) # Example: 'Broken pipe'
retval_code = errno.errorcode.get(retval_int, 'MODULEFAIL') # Ex: EPIPE
except:
## I don't expect to get here unless something broke in python errno...
retval_int = -1
retval_str = '__somethingswrong__'
retval_code = 'BADFAIL'
if debugmsg:
print "DEBUG: Can't {0}() on socket (errno:{1}, code:{2} / {3})".format(
op, retval_int, retval_code, retval_str)
return retval_int, retval_str, retval_code
connect_finished = False
while not connect_finished:
try:
c2s = socket(AF_INET, SOCK_STREAM) # Client to server socket...
# Set socket non-blocking
#fcntl.fcntl(c2s, fcntl.F_SETFL, os.O_NONBLOCK)
c2s.connect(('.'.join((SERVER_HOSTNAME, SERVER_DOMAIN,)), PORT))
c2s.setblocking(False)
assert c2s.gettimeout()==0.0, "c2s socket should be in non-blocking mode"
connect_finished = True
except socket_module.error, e:
errstr, errint, errcode = get_errno_info(e, op='connect',
debugmsg=DEBUG)
if errcode=='EINPROGRESS':
pass
to_srv_idx = 0
need_send_select = False
while True:
socket_list = [c2s]
# Get the list sockets which can: take input, output, etc...
if need_send_select:
# Only do this after send() EAGAIN or EWOULDBLOCK...
send_sock_list = socket_list
else:
send_sock_list = []
recv_ready_list, send_ready_list, exception_ready = select.select(
socket_list, send_sock_list, [])
for sock_fd in recv_ready_list:
assert sock_fd is c2s, "Strange socket failure here"
#incoming message from remote server
try:
from_srv_str = sock_fd.recv(1024, MSG_DONTWAIT)
except socket_module.error, e:
## https://stackoverflow.com/a/16745561/667301
errstr, errint, errcode = get_errno_info(e, op='recv',
debugmsg=DEBUG)
if errcode=='EAGAIN' or errcode=='EWOULDBLOCK':
# Busy, try again later...
print "recv() BLOCKED"
continue
elif errcode=='ECONNRESET' or errcode=='EPIPE':
# Server ended normally...
sys.exit(0)
## NOTE: if we get this far, we successfully received from_srv_str.
## Anything caught above, is some kind of fail...
print "from_srv_str: {0}".format(from_srv_str)
## Adding dynamic_list, per input from EJP, below...
if need_send_select is False:
dynamic_list = socket_list
else:
dynamic_list = send_ready_list
for sock_fd in dynamic_list:
# outgoing message to remote server
if sock_fd is c2s:
try:
to_srv_str = 'client->server {0}'.format(to_srv_idx)
sock_fd.send(to_srv_str, MSG_DONTWAIT)
##
time.sleep(1) ## Client blocks the server here... Why????
##
to_srv_idx += 1
need_send_select = False
except socket_module.error, e:
errstr, errint, errcode = get_errno_info(e, op='send',
debugmsg=DEBUG)
if errcode=='EAGAIN' or errcode=='EWOULDBLOCK':
## Try to send() later...
print "send() BLOCKED"
need_send_select = True
continue
elif errcode=='ECONNRESET' or errcode=='EPIPE':
# Server ended normally...
sys.exit(0)
Original Question Code:
tcp_server.py
#!/usr/bin/python -u
from socket import AF_INET, SOCK_STREAM, SO_REUSEADDR, SOL_SOCKET
#from socket import MSG_OOB <--- for send()
from socket import socket
import socket as socket_module
import select
import fcntl
import os
host = ''
port = 9997
serv_sock = socket(AF_INET, SOCK_STREAM)
serv_sock.setsockopt(SOL_SOCKET, SOCK_STREAM, 1)
serv_sock.bind((host, port))
serv_sock.listen(5)
fcntl.fcntl(serv_sock, fcntl.F_SETFL, os.O_NONBLOCK) # Make the socket non-blocking
sock_list = [serv_sock]
from_client_str = '__DEFAULT__'
to_client_idx = 0
loop_count = 0
while True:
recv_ready_list, send_ready_list, exception_ready = select.select(sock_list, sock_list,
[], 5)
print "---"
print "LOOP_COUNT", loop_count
## Read all sockets which are input-ready... might be client or server...
for sock_fd in recv_ready_list:
# accept() if we're reading on the server socket...
if sock_fd is serv_sock:
clientsock, clientaddr = sock_fd.accept()
sock_list.append(clientsock)
# read input from the client socket...
else:
try:
from_client_str = sock_fd.recv(4096)
if from_client_str=='':
# Client closed the socket...
print "CLIENT CLOSED SOCKET"
sock_list.remove(sock_fd)
except socket_module.error, e:
print "WARNING RECV FAIL"
print "from_client_str: '{0}'".format(from_client_str)
for sock_fd in send_ready_list:
if sock_fd is not serv_sock:
try:
to_client_str = "server->client: {0}\n".format(to_client_idx)
sock_fd.send(to_client_str)
to_client_idx += 1
except socket_module.error, e:
print "TO CLIENT SEND ERROR", e
loop_count += 1
tcp_client.py
#!/usr/bin/python -u
from socket import AF_INET, SOCK_STREAM
from socket import gethostname, socket
import socket as socket_module
import select
import fcntl
import errno
import time
import sys
import os
## NOTE: Using this script to simulate a scheduler
SERVER_HOSTNAME = 'myHostname'
SERVER_DOMAIN = 'mydomain.local'
PORT = 9997
def handle_socket_error_continue(e):
## non-blocking socket info from:
## https://stackoverflow.com/a/16745561/667301
print "HANDLE_SOCKET_ERROR_CONTINUE"
err = e.args[0]
if (err==errno.EAGAIN) or (err==errno.EWOULDBLOCK):
print 'CLIENT DEBUG: No data input from server'
return True
else:
print 'FROM SERVER RECV ERROR: {0}'.format(e)
sys.exit(1)
c2s = socket(AF_INET, SOCK_STREAM) # Client to server socket...
c2s.connect(('.'.join((SERVER_HOSTNAME, SERVER_DOMAIN,)), PORT))
# Set socket non-blocking...
fcntl.fcntl(c2s, fcntl.F_SETFL, os.O_NONBLOCK)
to_srv_idx = 0
while True:
socket_list = [c2s]
# Get the list sockets which can: take input, output, etc...
recv_ready_list, send_ready_list, exception_ready = select.select(
socket_list, socket_list, [])
for sock_fd in recv_ready_list:
assert sock_fd is c2s, "Strange socket failure here"
#incoming message from remote server
try:
from_srv_str = sock_fd.recv(4096)
except socket_module.error, e:
## https://stackoverflow.com/a/16745561/667301
err_continue = handle_socket_error_continue(e)
if err_continue is True:
continue
else:
if len(from_srv_str)==0:
print "SERVER CLOSED NORMALLY"
sys.exit(0)
## NOTE: if we get this far, we successfully received from_srv_str.
## Anything caught above, is some kind of fail...
print "from_srv_str: {0}".format(from_srv_str)
for sock_fd in send_ready_list:
#incoming message from remote server
if sock_fd is c2s:
#to_srv_str = raw_input('Send to server: ')
try:
to_srv_str = 'client->server {0}'.format(to_srv_idx)
sock_fd.send(to_srv_str)
##
time.sleep(1) ## Client blocks the server here... Why????
##
to_srv_idx += 1
except socket_module.error, e:
print "TO SERVER SEND ERROR", e
TCP sockets are almost always ready for writing, unless their socket send buffer is full.
It is therefore incorrect to always select on writability for a socket. You should only do so after you've encountered a send failure due to EAGAIN/EWOULDBLOCK. Otherwise your server will spin mindlessly processing writeable sockets, which will usually be all of them.
However, when I put a time.sleep(1) statement after the client does an
fd.send() to the server, the TCP server code intermittently pauses
while the client is sleeping.
AFAICT from running the provided code (nice self-contained example, btw), the server is behaving as intended.
In particular, the semantics of the select() call are that select() shouldn't return until there is something for the thread to do. Having the thread block inside select() is a good thing when there is nothing that the thread can do right now anyway, since it prevents the thread from spinning the CPU for no reason.
So in this case, your server program has told select() that it wants select() to return only when at least one of the following conditions is true:
serv_sock is ready-for-read (which is to say, a new client wants to connect to the server now)
serv_sock is ready-for-write (I don't believe this ever actually happens on a listening-socket, so this criterion can probably be ignored)
clientsock is ready-for-read (that is, the client has sent some bytes to the server and they are waiting in clientsock's buffer for the server thread to recv() them)
clientsock is ready-for-write (that is, clientsock has some room in its outgoing-data-buffer that the server could send() data into if it wants to send some data back to the client)
Five seconds have passed since the call to select() started blocking.
I see (via print-debugging) that when your server program blocks, it is blocking inside select(), which indicates that none of the 5 conditions above are being met during the blocking-period.
Why is that? Well, let's go down the list.
Not met because no other clients are trying to connect
Not met because this never happens
Not met because the server has read all of the data that the connected client has sent (and since the connected client is itself sleeping, it's not sending any more data)
Not met because the server has filled up the outgoing-data buffer of its clientsock (because the client program is sleeping, it's only reading the data coming from the server intermittently, and the TCP layer guarantees lossless/in-order transmission, so once clientsock's outgoing-data-buffer is full, clientsock won't select-as-ready-for-write unless/until the client reads at least some data from its end of the conenction)
Not met because 5 seconds haven't elapsed yet since select() started blocking.
So is this behavior actually a problem for the server? In fact it is not, because the server will still be responsive to any other clients that connect to the server. In particular, select() will still return right away whenever serv_sock or any other client's socket select()s as ready-for-read (or ready-for-write) and so the server can handle the other clients just fine while waiting for your hacked/slow client to wake up.
The hacked/slow client might be a problem for the user, but there's nothing the server can really do about that (short of forcibly disconnecting the client's TCP connection, or maybe printing out a log message requesting that someone debug the connected client program, I suppose :)).
I agree with EJP, btw -- selecting on ready-for-write should only be done on sockets that you actually want to write some data to. If you don't actually have any desire to write to the socket ASAP, then it's pointless and counterproductive to instruct select() to return as soon as that socket is ready-for-write: the problem with doing so is that you're likely to spin the CPU a lot whenever any socket's outgoing-data-buffer is less-than-full (which in most applications, is most of the time!). The user-visible symptom of the problem would be that your server program is using up 100% of a CPU core even when it ought to be idle or mostly-idle.
Im wondering is there any way to find out the socket that is open and then to close it?
For instance,I have a script "SendInfo.py" which opens a socket and sends some info over TCP.
If I call this script to run it e.g. "python SendInfo.py" , it will open a new socket.
If I run this script again using "python SendInfo.py", which will send some more up to date information, I would like to cancel the previous TCP transaction and start a new one - e.g. by closing the previous socket.
How do I get access to the open socket at the beginning of my script in order to close it? Ive tried looking into threads, but Im similarly confused about which threads are open and how to close open threads etc.
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.settimeout(2)
s.connect((self.__host, PORT))
I'm not sure if this is what you are after but here is a method of ensuring that the script is only running once and killing an existing running script.
You may find something useful in it. (This is for Linux)
#!/usr/bin/python
# running.py
# execute by making the script executable
# put it somewhere on $PATH and execute via running.py
# or execute via ./running.py
import os, sys, time , signal, socket
running_pid = os.popen('ps --no-headers -C running.py').read(5)
try:
running_pid = int(running_pid)
except:
running_pid = 0
current_pid = int(os.getpid())
if running_pid != 0:
if running_pid != current_pid:
print "Already running as process", running_pid
print "Killing process", running_pid
os.kill(int(running_pid), signal.SIGKILL)
# sys.exit()
# Create a listening socket for external requests
tcp_port = 5005
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
except:
print "Error on Socket 5005"
# force re-use of the socket if it is in time-out mode after being closed
# other wise we can get bind errors after closing and attempting to start again
# within a minute or so
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
try:
sock.settimeout(0.10)
sock.bind(("localhost", tcp_port))
except IOError as msg:
print "Error on Socket Bind "+str(tcp_port)+", running.py is probably already running"
pass
try:
sock.listen((1))
except:
print "Error on Socket listen"
time.sleep(60)
sock.close()
I am new to socket coding in Python, and I wrote this simple function to connect to a server. It runs in a tkinter window. I have an Entry widget, and it is where you input the IP address of the server to connect to. However, when you click the button to connect, the application hangs and freezes. Here is the code below.
def Test(self):
socket.setdefaulttimeout(5)
lengthInfo = self.lengthEntry.get()
if self.portEntry.get() != '':
portInfo = int(self.portEntry.get())
serverInfo = self.serverEntry.get()
conn = socket.socket()
if not self.portEntry.get():
portInfo = 80
try:
conn = socket.socket()
name = socket.gethostbyname(serverInfo)
conn.connect((name,portInfo))
ans = conn.recv(2048)
self.outputWindow.insert(END, "Connection successful: \n \
port:{}, server:{} ('{}'), '{}' \n".format(portInfo, name, serverInfo, \
ans))
return
except Exception as e:
self.outputWindow.insert(END, str(e) + "\n")
I originally thought it was because there was now timeout, but as you can see, I added a 5 second timeout in the very first line of the code. I assumed it was because the application was having some sort of trouble connecting, but I checked Windows task manager, and under the network section there was no activity. I also ran the program in Ubuntu 14.04 but got the same results.
Any solutions?
The socket waits for 2,048 bytes from the server (conn.recv(2048)) and I guess they never arrive.
I have trouble connecting to my own socket on localhost.
s.connect(('127.0.0.1', 4458)) (or "localhost") will just take forever,
and eventually timeout with TimeoutError: [Errno 110] Connection timed out
It should open port 4458, another script will then send some chars to it. Both scripts are supposed to run on the same Raspberry Pi, while 'server' one will execute with sudo (to access the GPIOs) and one without, being a chat bot.
I have no trouble running the server on the Pi (with python 3.4.1) and the client on my Laptop (mac, python 3.4.2).
Also it does work in reverse direction, server script on the laptop and client on the Raspberry.
As final test, it works with both, the server and the client on the said macbook.
Just server + client on the Pi does not work.
The program freezes
My shortened code if it helps:
# $ sudo python3 server.py
__author__ = 'luckydonald'
import socket # server
import time # wait for retry
import threading
class Server(threading.Thread):
port = 4458;
QUIT = False
def run(self):
s = socket.socket()
failed = True
print ("Starting Server on Port %d" % (self.port))
while failed:
try:
s.bind(("", self.port))
except Exception as err:
print(err)
print("Port assignment Failed. Retring in 1 second.")
time.sleep(1)
else:
failed = False
print("Success.")
while not self.QUIT:
print("Listening!")
conn, addr = s.accept() # freezes here
print("Got something: %s , %s" %(str(conn), str(addr)))
while not self.QUIT:
result = conn.recv(1)
print("Got result: " + str(result))
server = Server();
server.daemon = True
server.run();
# server.start();
And for the client:
# python3 cilent.py
s = socket.socket()
print("connecting...")
s.connect(("localhost",4458)) # also tried "172.0.0.1" # freezes here
print("connected!")
s.sendall("+".encode("utf-8"))
s.sendall("-".encode("utf-8"))
s.close()
It will result in this:
What I didn't expected was that localhost/127.0.0.1 did not work.
100% package loss
I had a malformatted entry in my hosts file.
You should check for below items
there is an installed internet information services
iis is running
firewall is grants required ports for running the python.exe
I'm trying to setup a RFCOMM client-server communication system between my PC and my Nokia E63. I'm using Python with PyBluez for setting up the server and using PyS60 to program the client on my phone.
However PyBluez is not accepting the connection.
Here the code for the server:
from bluetooth import *
server_sock=BluetoothSocket( RFCOMM )
server_sock.bind(("",PORT_ANY))
server_sock.listen(1)
port = server_sock.getsockname()[1]
uuid = "94f39d29-7d6d-437d-973b-fba39e49d4ee"
advertise_service( server_sock, "SampleServer",
service_id = uuid,
service_classes = [ uuid, SERIAL_PORT_CLASS ],
profiles = [ SERIAL_PORT_PROFILE ],
# protocols = [ OBEX_UUID ]
)
print "Waiting for connection on RFCOMM channel %d" % port
client_sock, client_info = server_sock.accept()
print "Accepted connection from ", client_info
try:
while True:
data = client_sock.recv(1024)
if len(data) == 0: break
print "received [%s]" % data
except IOError:
pass
print "disconnected"
client_sock.close()
server_sock.close()
print "all done"
And here is the code for the client
#!/usr/bin/env python
import socket
class BTReader:
def connect(self):
self.sock=socket.socket(socket.AF_BT, socket.SOCK_STREAM)
addr, services=socket.bt_discover()
print "Discovered: %s, %s" % (addr, services)
port = services[services.keys()[0]]
print port
address=(addr,port)
print "Connecting to", str(address), "..."
self.sock.connect(address)
print "OK."
data = "Hello, World!"
print "Sending data:", data
self.sock.send("Hello World!");
print "SENT."
def close(self):
self.sock.close()
def main():
bt=BTReader()
bt.connect()
bt.close()
if __name__ == '__main__':
main()
When I run both the programs I get this output
1) Server (PC):
Waiting for connection on RFCOMM channel 1 [And it stays there. It doesn't acknowledge the connection. I've checked using WINPDB, even after the phone shows that it has established a connection, the server script remains in the server_sock.accept() loop.]
2) Client (phone):
Discoverd: xx:xx:xx:xx:xx:xx {u'SampleServer':1}
1
Connecting to ('xx:xx:xx:xx:xx:xx', 1) ...
OK.
Sending data: Hello World!
Traceback (most recent call last):
...
...
File "c;\resource\socket.py" , line 409, in send return self._sock.send(data, f, cb)
error: (0, 'Error')
What is causing the problem ??
I know its a year later, but I have another solution. On certain versions of Debian (Raspbian etc) and maybe some others distros. The server_sock.accept() will by default just hang and never accept a connection - even from a paired device! However, a solution to this is really simple. If you go to /etc/bluetooth/main.conf there is a line which is called Disable Plugins. Add a line or change so it looks like this:-
DisablePlugins = pnat
Then restart the Bluetooth service:-
sudo invoke–rc.d bluetooth restart
It now MAY have been fixed.
Good luck!
Reference: RFCOMM without pairing using PyBluez on Debian?
You should re-read the Rfcomm-client.py example of the PyBluez library.
I don't know why you are using some random socket instead of the BluetoothSocket object...
However I suspect that is the error. To detail for further readers:
If you look at the client code, he was importing the socket module and using that - that has NOTHING to do with pybluez and is wrong.
As a hint, try to make the 2 examples in the PyBluez library work (client and server) and then make your application.
Sometimes the server pops a window and asks the user to approve the connection. If you run without an X-server then you don't have the chance to see the dialog window and the connection is refused..!! (have spent half a day in the past on this...!!!)