I have been working on making my own cloud storage, but after receiving my file data, it doesn't break the while-loop. It does not proceed to the print statement where it says the file has been downloaded and waits for more data from the server.
Here is the code part where it receives the file data:
if console == "download":
s.send(bytes("download","utf-8"))
file_name = input("Enter the file name: ")
s.send(bytes(file_name,"utf-8"))
print(f"[DOWNLOADING] Downloading {file_name}")
f = open(file_name,'wb')
while(True):
l = s.recv(1024)
f.write(l)
if not l:
break
print(f"[DOWNLOADED] Downloaded {file_name}")
socket.recv is a blocking call.
socket.recv(1024) will read at most 1024 bytes, blocking if no data is waiting to be read. If you don't read all data, an other call to socket.recv won't block.
socket.recv will also end with an empty string if the connection is closed or there is an error.
If you want a non-blocking socket, you can use the select module (a bit more complicated than just using sockets) or you can use socket.setblocking.
Related
I am trying to write a simple Python script that connects to a number of Fluke Thermo-Hygrometers (DewK 1620A) and write the temperature and humidity readings to a file I can then ingest into Splunk. This is the first time I've ever tried anything with Python and I'm really close, but can't seem to nail down how to get the data via a TCP socket.
Overview
The script reads a list of devices from an external JSON and then opens a connection to each device, sends a command to get the current readings, and then writes those readings to a file.
In my first iteration, I simply made a single "data = s.recv(64)" call, but the devices were inconsistent in returning a full result. Sometimes I'd get the full result (ie. "69.64,45.9,0,0") and other times I'd only get part of the reading (ie. "69.64,4").
While True Loop
After doing some research, I began to see recommendations for using a while True loop to get the "rest" of the data in a second (or third) pass. I changed out my simple s.recv call with the following:
while True:
data = s.recv(64) # Retrieve data from device
if not data: # If no data exists, break loop
continue
f.write(data.decode()) # Write data to logfile
Unfortunately, now the script will not finish. I suspect the loop is not exiting, but the response should never be more than 24 bytes. I'm not sure how else to test and exit the loop. I tried adding a timeout, but that kills the whole script.
connectDeviceTCP.py
import datetime
import json
import socket
# the command to be passed to the device
command = "read?\r"
# open the deviceLocation.json file for reading
jsonFile = open("devices.json", "r", encoding="utf-8")
# load the contents of the json file into
locationFile = json.load(jsonFile)
jsonFile.close()
# for each device, connect & retrieve device readings
for device in locationFile["devices"]:
location = device["location"]
host = device["host"]
portStr = device["port"]
# convert the portStr variable from string to integer
port = int(portStr)
# open log file for appending.
f = open("log/" + location + ".log", "a")
try:
# create a socket on client using TCP/IP
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
# set socket timeout to 3 seconds
s.settimeout(10)
# connect to host and port
s.connect((host, port))
except TimeoutError:
# write to the log file if the host cannot be reached
f.write(('\n{:%Y-%m-%d %H:%M:%S} - '.format(datetime.datetime.now())) + location + " - Error: " + host + ":" + portStr + " does not respond.")
else:
# send the command to the device
s.sendall(command.encode())
# write the timestamp and location to the log
f.write(('{:%Y-%m-%d %H:%M:%S} - '.format(datetime.datetime.now())) + location + " - ")
while True:
data = s.recv(64) # Retrieve data from device
if not data: # If no data exists, break loop
break
f.write(data.decode()) # Write data to logfile
# --- The following work except the device doesn't always spit out all the data.
# receive message string from device
#data = s.recv(64)
# write returned values to log file.
#f.write(data.decode())
finally:
# disconnect the client
s.close()
# close log file
f.close()
The devices communicate line-oriented with lines terminated by \r, so just read a whole line - replace the while True loop with
data = s.makefile(newline='\r').readline()
f.write(data) # Write data to logfile
The following codes let me download from server to client three files called tmp.bsp, tmp.seq and tmp.dms. However, just the first file tmp.dms is completely downloaded. The other one tmp.seq is filled up with the informations of tmp.bsp and tmp.bsp stay 0KB.
client:
import socket
import socket
skClient = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
skClient.connect(("127.0.0.1",2525))
sData = "Temp"
sData2 = "Temp"
sData3 = "Temp"
while True:
sData = skClient.recv(1024)
fDownloadFile = open("tmp.dms","wb")
sData2 = skClient.recv(1024)
fDownloadFile2 = open("tmp.seq","wb")
sData3 = skClient.recv(1024)
fDownloadFile3 = open("tmp.bsp","wb")
while sData:
fDownloadFile.write(sData)
sData = skClient.recv(1024)
fDownloadFile.close()
fDownloadFile2.write(sData2)
sData2 = skClient.recv(1024)
fDownloadFile2.close()
fDownloadFile3.write(sData3)
sData3 = skClient.recv(1024)
fDownloadFile3.close()
print "Download over"
break
skClient.close()
n is a counter and the prints are for debugging.
sFileName is to download one file, and used to work but since I want three files I just commented it.
server:
import socket
host = ''
skServer = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
skServer.bind((host,2525))
skServer.listen(10)
print "Server currently active"
while True:
Content,Address = skServer.accept()
print Address
files = "C:\Users\Name_user\Desktop\Networking\Send_Receive/"
fUploadFile = open(files+str('tmp.dms'),"rb")
sRead = fUploadFile.read(1024)
fUploadFile2 = open(files+str('tmp.seq'),"rb")
sRead2 = fUploadFile2.read(1024)
fUploadFile3 = open(files+str('tmp.bsp'),"rb")
sRead3 = fUploadFile3.read(1024)
while sRead:
Content.send(sRead)
sRead = fUploadFile.read(1024)
Content.send(sRead2)
sRead2 = fUploadFile2.read(1024)
# Content.send(sRead3)
# sRead3 = fUploadFile3.read(1024)
Content.close()
print "Sending is over"
break
skServer.close()
files I'm using:
server2.py is my server
Execution
The main issue with your code is that you're sending / receiving an arbitrary number of data. If your buffer (1024) is smaller than the file size then the client's file will contain less information, and if it's larger the file may contain more information (data from the next file).
You could solve this issue by sending a value that signifies the end of a file. The problem with this method is that this value can't be contained in any file, and the client must be scanning the received data for this value.
Another possible solution is to calculate the file size and send that infomation in front of the file data. This way the cilent will know how many data to expect for each file.
Using struct.pack we can create a minimal four bytes header with the file size.
def send_file(soc, path):
with open(path, 'rb') as f:
data = f.read()
size = struct.pack('!I', len(data))
soc.send(size + data)
Tthen the client can get the file size by reading four bytes and unpacking to int.
def recv_file(soc, path):
size_header = soc.recv(4)
size = struct.unpack('!I', size_header)[0]
data = soc.recv(size)
with open(path, 'wb') as f:
f.write(data)
Note that sending/receiving files with one call may raise a socket error if the file size is larger than the socket buffer. In that case you'll have to read the data in smaller chunks in a loop, or increase the buffer size with socket.setsockopt.
Here is a modified version of the above functions that can handle large files:
import struct
import os.path
def send_file(soc, path):
file_size = os.path.getsize(path)
size_header = struct.pack('!Q', file_size)
soc.send(size_header)
with open(path, 'rb') as f:
while True:
data = f.read(1024)
if not data:
break
soc.send(data)
def recv_file(soc, path):
size_header = soc.recv(8)
file_size = struct.unpack('!Q', size_header)[0]
chunks = [1024 for i in range(file_size / 1024)]
with open(path, 'wb') as f:
for chunk in chunks:
f.write(soc.recv(chunk))
f.write(soc.recv(file_size % 1024))
I haven't tested this code thoroughly, but it should work for files of any size.
An example using the send_file function in your server:
host = ''
skServer = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
skServer.bind((host,2525))
skServer.listen(10)
print "Server currently active"
Content,Address = skServer.accept()
print Address
files = ['tmp.bsp', 'tmp.seq', 'tmp.dms']
for file in files:
send_file(Content, file)
Content.close()
print "Sending is over"
skServer.close()
Using recv_file in the client:
skClient = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
skClient.connect(("127.0.0.1",2525))
files = ['tmp.bsp', 'tmp.seq', 'tmp.dms']
for file in files:
recv_file(skClient, file)
print "Download over"
skClient.close()
Yes you are right, I did run your program and found exactly same issue. I dont have enough time to work more on this issue but I found few key points which might lead you to the right work around.
https://docs.python.org/2/howto/sockets.html
The above official doc says:
When a recv returns 0 bytes, it means the other side has closed (or is in the process of closing) the connection. You will not receive any more data on this connection. Ever. You may be able to send data successfully
This is what it is happening when the third file returns 0 bytes.
But why 2nd and 3rd file is merged, I guess its because sockets are just buffered files and we might need to try making sure buffer is clear before sending another.
Read this,
Now there are two sets of verbs to use for communication. You can use send and recv, or you can transform your client socket into a file-like beast and use read and write. The latter is the way Java presents its sockets. I’m not going to talk about it here, except to warn you that you need to use flush on sockets. These are buffered “files”, and a common mistake is to write something, and then read for a reply. Without a flush in there, you may wait forever for the reply, because the request may still be in your output buffer.
But if you plan to reuse your socket for further transfers, you need to realize that there is no EOT on a socket. I repeat: if a socket send or recv returns after handling 0 bytes, the connection has been broken. If the connection has not been broken, you may wait on a recv forever, because the socket will not tell you that there’s nothing more to read (for now). Now if you think about that a bit, you’ll come to realize a fundamental truth of sockets: messages must either be fixed length (yuck), or be delimited (shrug), or indicate how long they are (much better), or end by shutting down the connection. The choice is entirely yours, (but some ways are righter than others).
Hope this helps.
I'm not totally fluent in Python, but I think your while statement should be something like:
while: sData or sData2 or sData3
I may have the syntax wrong, but currently it looks like you will stop when "sData" is done and stop downloading sData2 and aData3 at that time even if they haven't finished.
Hmm--either that or the "While" isn't looping at all and it's just being used as an "if"? hard to tell without knowing the API.
I'm trying to write a Python program that can browse directories and grab files w/ sockets if the client connects to the server. The browsing part works fine, it prints out all directories of the client.
Here's a part of the code:
with clientsocket:
print('Connected to: ', addr)
while True:
m = input("Command > ")
clientsocket.send(m.encode('utf-8'))
data = clientsocket.recv(10000)
if m == "exit":
clientsocket.close()
if m.split()[0] == 'get':
inp = input("Filename > ")
while True:
rbuf = clientsocket.recv(8192)
if not rbuf:
break
d = open(inp, "ab")
d.write(rbuf)
d.close()
elif data.decode('utf-8').split()[0] == "LIST":
print(data.decode('utf-8'))
if not data:
break
However, the problem lies in here:
if m.split()[0] == 'get':
inp = input("Filename > ")
while True:
rbuf = clientsocket.recv(8192)
if not rbuf:
break
It seems to be stuck in an infinite loop. What's more interesting is that the file I'm trying to receive is 88.3kb, but what the file returns is 87kb while it's in the loop, which is very close...
I tried receiving a python script at one time as well (without the loop) and it works fine.
Here's some of the client code:
while True:
msg = s.recv(1024).decode('utf-8')
if msg.split()[0] == "list":
dirs = os.listdir(msg.split()[1])
string = ''
for dira in dirs:
string += "LIST " + dira + "\n"
s.send(string.encode('utf-8'))
elif msg == "exit":
break
else:
#bit that sends the file
with open(msg.split()[1], 'rb') as r:
s.sendall(r.read())
So my question is, why is it getting stuck in an infinite loop if I have it set up to close when there is no data, and how can I fix this?
I'm sort of new to network programming in general, so forgive me if I miss something obvious.
Thanks!
I think I know what's the problem, but I may be wrong. It happened to me several times, that the entire message is not received in one recv call, even if I specify the correct length. However, you don't reach the end of stream, so your program keeps waiting for remaining of 8192 bytes which never arrives.
Try this:
Sending file:
#bit that sends the file
with open(msg.split()[1], 'rb') as r:
data = r.read()
# check data length in bytes and send it to client
data_length = len(data)
s.send(data_length.to_bytes(4, 'big'))
s.send(data)
s.shutdown(socket.SHUT_RDWR)
s.close()
Receiving the file:
# check expected message length
remaining = int.from_bytes(clientsocket.recv(4), 'big')
d = open(inp, "wb")
while remaining:
# until there are bytes left...
# fetch remaining bytes or 4094 (whatever smaller)
rbuf = clientsocket.recv(min(remaining, 4096))
remaining -= len(rbuf)
# write to file
d.write(rbuf)
d.close()
There are several issues with your code.
First:
clientsocket.send(m.encode('utf-8'))
data = clientsocket.recv(10000)
This causes the file to be partially loaded to data variable when you issue get statement. That's why you don't get full file.
Now this:
while True:
rbuf = clientsocket.recv(8192)
if not rbuf:
break
...
You indeed load full file but the client never closes the connection (it goes to s.recv() after sending the file) so if statement is never satisfied. Thus this loop gets blocked on the clientsocket.recv(8192) part after downloading the file.
So the problem is that you have to somehow notify the downloader that you've sent all the data even though the connection is still open. There are several ways to do that:
You calculate the size of the file and send it as a first few bytes. For example, say the content of the file is ala ma kota. These are 11 bytes and thus you send \x11ala ma kota. Now receiver knows that first byte is size and it will interpret it as such. Of course one byte header isn't much (you would only be able to send max 256 byte files) so normally you go for for example 4 bytes. So now your protocol between client and server is: first 4 bytes is the size of the file. Thus our initial file would be sent as \x0\x0\x0\x11ala ma kota. The drawback of this solution is that you have to know the size of the content before sending it.
You mark the end of the stream. So you pick a particular character, say X and you read the straem until you find X. If you do then you know that the other side sent everything it has. The drawback is that if X is in the content then you have to escape it, i.e. additional content processing (and interpretation on the other side) is needed.
Ok, I have a socket and I'm handling one line at a time and logging it. The code below works great for that. The cout function is what I use to send data to the log. The for loop I use so I can process one line at a time.
socket.connect((host, port))
readbuffer = ""
while True:
readbuffer = readbuffer+socket.recv(4096).decode("UTF-8")
cout("RECEIVING: " + readbuffer) #Logs the buffer
temp = str.split(readbuffer, "\n")
readbuffer=temp.pop( )
for line in temp:
#Handle one line at a time.
The I ran into a problem where when the server disconnected me, all of the sudden I had a massive file full of the word "RECEIVING: ". I know this is because when a python socket disconnects the socket starts receiving blank data constantly.
I have tried inserting:
if "" == readbuffer:
print("It disconnected!")
break
All that did was immediately break the loop, and say that it disconnected, even on a successful connection.
I also know that I can detect a disconnection by sending data, but I can't do that, because anything I send gets broadcasted to all the other clients on the server, and this is meant to debug those clients so I it would interfere.
What do I do. Thank you in advanced.
You need to check the result of the recv() separately to the readbuffer
while True:
c = socket.recv(4096)
if c == '': break # no more data
readbuffer = readbuffer + c.decode("UTF-8")
...
I am not sure if this topic have been answered or not, if was I am sorry:
I have a simple python script the sends all files in one folder:
Client:
import os,sys, socket, time
def Send(sok,data,end="292929"):
sok.sendall(data + end);
def SendFolder(sok,folder):
if(os.path.isdir(folder)):
files = os.listdir(folder);
os.chdir(folder);
for file_ in files:
Send(sok,file_);#Send the file name to the server
f = open(file_, "rb");
while(True):
d = f.read();#read file
if(d == ""):
break;
Send(sok, d, "");#Send file data
f.close();
time.sleep(0.8);#Problem here!!!!!!!!!!!
Send(sok,"");#Send termination to the server
time.sleep(1);#Wait the server to write the file
os.chdir("..");
Send(sok,"endfile");#let the server know that we finish sending files
else:
Send("endfile")#If not folder send termination
try:
sok1 = socket.socket();
sok1.connect(("192.168.1.121",4444))#local ip
time.sleep(1);
while(True):
Send(sok1,"Enter folder name to download: ");
r = sok1.recv(1024);
SendFolder(sok1,r);
time.sleep(0.5);
except BaseException, e:
print "Error: " + str(e);
os._exit(1);
Server:
import sys,os,socket,time
# receive data
def Receive(sock, end="292929"):
data = "";
while(True):
if(data.endswith(end)):
break;
else:
data = sock.recv(1024);
return data[:-len(end)];#return data less termination
def FolderReceive(sok):
while(True):
r = Receive(sok);# recv filename or folder termination("endfile")
if(r == "endfolder"):
print "Folder receive complete.";
break;
else:
filename = r;#file name
filedata = Receive(sok);# receive file data
f = open(filename,"wb");
f.write(filedata);
f.close();#finish to write the file
print "Received: " + filename;
try:
sok1 = socket.socket();
sok1.bind(("0.0.0.0",4444));
sok1.listen(5);
cl , addr = sok1.accept();#accepts connection
while(True):
r = Receive(cl);
sys.stdout.write("\n" + r);
next = raw_input();
cl.sendall(next);#send folder name to the client
FolderReceive(cl);
except BaseException, e:
print "Error: " + str(e);
os._exit(1);
I know this not best server ever...but is what I know. This just work for a folder with small files because if I send big files(like 5mb...) it crashes because the time the client waits for the server is not enough.
So my question is how can I send the files to the server without client need to wait??or know exactly how many time the client needs to wait for the server to receive the file?? Some code that does the same but handling any file size, any help?
TCP sockets are byte streams, not message streams. If you want to send a series of separate messages (like your separate files), you need to define a protocol, and then write a protocol handler. There is no way around that; just guessing at the timing or trying to take advantage of packet boundaries cannot possibly work.
The blog post linked above shows one way to do it. But you can do it with string delimiters if you want. But you have to deal with two problems:
The delimiter can appear anywhere in a read packet, not just at the end.
The delimiter can be split on packet boundaries—you may get "2929" at the end of one read, and the other "29" at the start of the next.
The usually way you do that is to accumulate a buffer, and search for the delimiter anywhere in the buffer. Something like this:
def message(sock, delimiter):
buf = ''
while True:
data = sock.read(4096)
if not data:
# If the socket closes with no delimiter, this will
# treat the last "partial file" as a complete file.
# If that's not what you want, just return, or raise.
yield buf
return
buf += data
messages = buf.split(delimiter)
for message in messages[:-1]:
yield message
buf = message[-1]
Meanwhile, you have another problem with your delimiter: There's nothing stopping it from appearing in the files you're trying to transmit. For example, what if you tried to send your script, or this web page?
That's one of the reasons that other protocols are often better than delimiters, but this isn't hard to deal with: just escape any delimiters found in the files. Since you're sending the whole file at once, you can just use replace on right before the sendall, and the reverse replace right before the split.