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Error status after sending 32768 bytes from serial port in Python

I am making uart communication using serial library. I can send and receive data, but when the number of bytes sent reaches 32768 or more, I get the error;
ValueError: byte must be in range(0,256)
function definition:
def Write_to_serial_port(value):
ser.write([value])
function usage:
#...
for i in data_buf[0:total_len]: # data_buf is a list
Write_to_serial_port(i)
#...
The error message that occurs when the number of bytes sent reaches 32768:
An alternative serial port write function I tested:
def Write_to_serial_port(value):
data = struct.pack('>B', value)
ser.write(data)
Again the error message that occurs when the number of bytes sent reaches 32768:
I also tried periodically flushing the input and output buffers, but it didn't help.
Any ideas on the solution?
EDIT1:
The purpose of the program is to send the bytes in the binary file. While doing this, I send 128 bytes (from the binary file) and 13 bytes of CRC, file size etc information over the serial port in each cycle. data_buff size is 255 bytes but I am using 141 bytes.
function usage(Extended):
# ...
# Some definitions and assignments
# ...
while(bytes_remaining):
if(bytes_remaining >= 128):
len_to_read = 128
else:
len_to_read = bytes_remaining
for x in range(len_to_read):
file_read_value = bin_file.read(1)
data_buf[9+x] = int(file_read_value[0])
data_buf[0] = mem_write_cmd_total_len-1
data_buf[1] = write_cmd
data_buf[2] = word_to_byte(base_mem_address,1,1)
data_buf[3] = word_to_byte(base_mem_address,2,1)
data_buf[4] = word_to_byte(base_mem_address,3,1)
data_buf[5] = word_to_byte(base_mem_address,4,1)
data_buf[6] = gl_bin_file_sector_needed
data_buf[7] = len_to_read
data_buf[8] = send_count
send_count = send_count + 1
crc32 = get_crc(data_buf,mem_write_cmd_total_len - 4)
data_buf[9 +len_to_read] = word_to_byte(crc32,1,1)
data_buf[10+len_to_read] = word_to_byte(crc32,2,1)
data_buf[11+len_to_read] = word_to_byte(crc32,3,1)
data_buf[12+len_to_read] = word_to_byte(crc32,4,1)
for i in data_buf[0:mem_write_cmd_total_len]:
Write_to_serial_port(i)
#...
Error Message
EDIT2: I also tried splitting the 40KB binary file into 128byte chunk files and sending it. But I got the same error on the 256th file. I guess 256*128 = 32768 can't be a coincidence.

Receive UDP packet from specific source

I am trying to measure the responses back from DNS servers. Making a sniffer for a typical DNS response that is less than 512 bytes is no big deal. My issue is receiving large 3000+ byte responses - in some cases 5000+ bytes. I haven't been able to get a socket working that can receive that data reliably. Is there a way with Python sockets to receive from a specific source address?
Here is what I have so far:
import socket
import struct
def craft_dns(Qdns):
iden = struct.pack('!H', randint(0, 65535))
QR_thru_RD = chr(int('00000001', 2)) # '\x01'
RA_thru_RCode = chr(int('00100000', 2)) # '\x00'
Qcount = '\x00\x01' # question count is 1
ANcount = '\x00\x00'
NScount = '\x00\x00'
ARcount = '\x00\x01' # additional resource count is 1
pad = '\x00' #
Rtype_ANY = '\x00\xff' # Request ANY record
PROtype = '\x00\x01' # Protocol IN || '\x00\xff' # Protocol ANY
DNSsec_do = chr(int('10000000', 2)) # flips DNSsec bit to enable
edns0 = '\x00\x00\x29\x10\x00\x00\x00\x00\x00\x00\x00' # DNSsec disabled
domain = Qdns.split('.')
quest = ''
for x in domain:
quest += struct.pack('!B', len(x)) + x
packet = (iden+QR_thru_RD+RA_thru_RCode+Qcount+ANcount+NScount+ARcount+
quest+pad+Rtype_ANY+PROtype+edns0) # remove pad if asking <root>
return packet
def craft_ip(target, resolv):
ip_ver_len = int('01000101', 2) # IPvers: 4, 0100 | IP_hdr len: 5, 0101 = 69
ipvers = 4
ip_tos = 0
ip_len = 0 # socket will put in the right length
iden = randint(0, 65535)
ip_frag = 0 # off
ttl = 255
ip_proto = socket.IPPROTO_UDP # dns, brah
chksm = 0 # socket will do the checksum
s_addr = socket.inet_aton(target)
d_addr = socket.inet_aton(resolv)
ip_hdr = struct.pack('!BBHHHBBH4s4s', ip_ver_len, ip_tos, ip_len, iden,
ip_frag, ttl, ip_proto, chksm, s_addr, d_addr)
return ip_hdr
def craft_udp(sport, dest_port, packet):
#sport = randint(0, 65535) # not recommended to do a random port generation
udp_len = 8 + len(packet) # calculate length of UDP frame in bytes.
chksm = 0 # socket fills in
udp_hdr = struct.pack('!HHHH', sport, dest_port, udp_len, chksm)
return udp_hdr
def get_len(resolv, domain):
target = "10.0.0.3"
d_port = 53
s_port = 5353
ip_hdr = craft_ip(target, resolv)
dns_payload = craft_dns(domain) # '\x00' for root
udp_hdr = craft_udp(s_port, d_port, dns_payload)
packet = ip_hdr + udp_hdr + dns_payload
buf = bytearray("-" * 60000)
recvSock = socket.socket(socket.PF_PACKET, socket.SOCK_RAW, socket.ntohs(0x0800))
recvSock.settimeout(1)
sendSock = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
sendSock.settimeout(1)
sendSock.connect((resolv, d_port))
sendSock.send(packet)
msglen = 0
while True:
try:
pkt = recvSock.recvfrom(65535)
msglen += len(pkt[0])
print repr(pkt[0])
except socket.timeout as e:
break
sendSock.close()
recvSock.close()
return msglen
result = get_len('75.75.75.75', 'isc.org')
print result
For some reason doing
pkt = sendSock.recvfrom(65535)
Recieves nothing at all. Since I'm using SOCK_RAW the above code is less than ideal, but it works - sort of. If the socket is extremely noisy (like on a WLAN), I could end up receiving well beyond the DNS packets, because I have no way to know when to stop receiving packets when receiving a multipacket DNS answer. For a quiet network, like a lab VM, it works.
Is there a better way to use a receiving socket in this case?
Obviously from the code, I'm not that strong with Python sockets.
I have to send with SOCK_RAW because I am constructing the packet in a raw format. If I use SOCK_DGRAM the custom packet will be malformed when sending to a DNS resolver.
The only way I could see is to use the raw sockets receiver (recvSock.recv or recvfrom) and unpack each packet, look if the source and dest address match within what is supplied in get_len(), then look to see if the fragment bit is flipped. Then record the byte length of each packet with len(). I'd rather not do that. It just seems there is a better way.

Ok I was stupid and didn't look at the protocol for the receiving socket. Socket gets kind of flaky when you try to receive packets on a IPPROTO_RAW protocol, so we do need two sockets. By changing to IPPROTO_UDP and then binding it, the socket was able to follow the complete DNS response over multiple requests. I got rid of the try/catch and the while loop, as it was no longer necessary and I'm able to pull the response length with this block:
recvSock = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_UDP)
recvSock.settimeout(.3)
recvSock.bind((target, s_port))
sendSock = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
#sendSock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sendSock.settimeout(.3)
sendSock.bind((target, s_port))
sendSock.connect((resolv, d_port))
sendSock.send(packet)
pkt = recvSock.recvfrom(65535)
msglen = len(pkt[0])
Now the method will return the exact bytes received from a DNS query. I'll leave this up in case anyone else needs to do something similar :)

Python Requests/urllib — monitoring bandwidth usage

I want to log the total bytes downloaded and uploaded by my Python script.
total_downloaded_bytes = 0
def bandwidth_hook(r, *args, **kwargs):
global total_downloaded_bytes
total_downloaded_bytes += len(r.content)
req = requests.session()
req.hooks = {'response': bandwidth_hook}
The above code doesn't take into account HTTP compression (if I'm right) and the size of headers.
Is there a way to count total uploaded and downloaded bytes from a requests.session? If not, what about a script-wide count?

You can access the r.request object to calculate outgoing bytes, and you can determine incoming bytes (compressed or not) by looking at the content-length header for the incoming request. This should suffice for 99% of all requests you normally would make.
Calculating the byte size of headers is easy enough; just add up key and value lenghts, add 4 bytes for the colon and whitespace, plus 2 more for the blank line:
def header_size(headers):
return sum(len(key) + len(value) + 4 for key, value in headers.items()) + 2
There is also the initial line; that's {method} {path_url} HTTP/1.1{CRLF} for requests, and HTTP/1.x {status_code} {reason}{CRLF} for the response. Those lengths are all also available to you.
Total size then is:
request_line_size = len(r.request.method) + len(r.request.path_url) + 12
request_size = request_line_size + header_size(r.request.headers) + int(r.request.headers.get('content-length', 0))
response_line_size = len(r.response.reason) + 15
response_size = response_line_size + header_size(r.headers) + int(r.headers.get('content-length', 0))
total_size = request_size + response_size

Python UDP SocketServer can't read whole packet

At sender side I have the following code using processing language (portion code):
udp = new UDP( this, 6002 ); // create a new datagram connection on port 6000
//udp.log( true ); // <-- printout the connection activity
udp.listen( true ); // and wait for incoming message
escribeUDPLog3(1,TRANSMIT,getTime()); //call function
int[] getTime(){
int year = year();
int month = month()
int day = day();
int hour = hour();
int minute = minute();
int second = second();
int[] time_constructed = {year, month,day,hour,minute,second};
return time_constructed;
}
void escribeUDPLog3(int pkg_type, int state, int[] time){
short year = (short)(time[0]); //>> 8;
byte year_msb = byte(year >> 8);
byte year_lsb = byte(year & 0x00FF);
byte month = byte(time[1]);
byte day = byte(time[2]);
byte hour = byte(time[3]);
byte minute = byte(time[4]);
byte second = byte(time[5]);
byte[] payload = {byte(pkg_type), byte(state), year_msb, year_lsb, month, day, hour, minute,second};
try {
if (UDP5_flag) {udp.send(payload, UDP5_IP, UDP5_PORT);}
}
catch (Exception e) {
e.printStackTrace();
}
}
At receiver side I'm using SocketServer python structure to set up a server listening for udp datagrams, as following.
from datetime import datetime
import csv
import SocketServer
def nodeStateCheckout(nodeid, state, nodeState):
if (state == ord(nodeState)):
return "OK"
else:
return "FAIL"
def timeConstructor(time):
year = str(ord(time[0]) << 8 | ord(time[1]))
month = str(ord(time[2]))
day = str(ord(time[3]))
hour = str(ord(time[4]))
minute = str(ord(time[5]))
second = str(ord(time[6]))
time_formatted = year + "-" + month + "-" + day \
+ " " + hour + ":" + minute + ":" + second
return time_formatted
class MyUDPHandler(SocketServer.BaseRequestHandler):
"""
This class works similar to the TCP handler class, except that
self.request consists of a pair of data and client socket, and since
there is no connection the client address must be given explicitly
when sending data back via sendto().
"""
def handle(self):
try:
data = self.request[0].strip()
socket = self.request[1]
#print "{} wrote:".format(self.client_address[0])
pkg_type = ord(data[0])
if pkg_type == 1: # log 3
state = ord(data[1])
csvfile = open("log3.csv", "a+")
csvwriter = csv.writer(csvfile, delimiter=',')
time_reconstructed = timeConstructor(data[2:9])
if state == 3:
csvwriter.writerow(["STOP",time_reconstructed])
elif state == 2:
csvwriter.writerow(["START",time_reconstructed])
else:
print "unknown state"
csvfile.close()
else:
print "packet not known"
except IndexError:
print "Bad parsed byte"
if __name__ == "__main__":
HOST, PORT = "localhost", 8892
server = SocketServer.UDPServer((HOST, PORT), MyUDPHandler)
server.serve_forever()
Edited:
I have problem specifically when using timeConstructor(data[2:9]), because I'm accessing out of index data, sometimes (with the help of print) I can't received second byte from data, and one time it get me out of index because I didn't received minute and second. Most of the time the code works well, but this type of error get me curious.
Old:
The problem is when reading the payload, sometimes its seems that some bytes doesn't arrive, even when I captured the whole payload using Wireshark (but Wireshark didn't tell me if this is the sent packet or received packet because I'm using loopback interfaces, maybe duplicated info?). If the datagram has 16 bytes payload long, sometimes I received 15 because when parsing from data I get out of index error.
I think that there are some buffer problems. Isn't it? How to configured it properly? I know that I can get packet loss because of connectionless protocol but I dont think that bytes get lost. It is supposed that "data" has all payload data from one udp datagram.

I believe your problem is that socket.sendto() does not always send all the bytes that you give it. It returns the number of bytes sent and you may have to call it again. You might be better off with opening the socket yourself and calling socket.sendall()

Raw socket python packet sniffer

I have created a simple RAW socket based packet sniffer. But when I run it, it rarely captures up a packet. First I created this to capture packets in 1 second time intervals, but seeing no packets are captured I commented that line. I was connected to internet and a lot of http traffic are going here and there, but I could not capture a one. Is there a problem in this in the code where I created the socket? Please someone give me a solution. I am fairly new to python programming and could not understand how to solve this.
import socket, binascii, struct
import time
sock = socket.socket(socket.PF_PACKET, socket.SOCK_RAW, socket.htons(0x800))
print "Waiting.."
pkt = sock.recv(2048)
print "received"
def processEth(data):
#some code to process source mac and dest. mac
return [smac, dmac]
def processIP(data):
sip = str(binascii.hexlify(data[1]))
dip = str(binascii.hexlify(data[2]))
return [sip, dip]
def processTCP(data):
sport = str(data[0])
dport = str(data[1])
return [sport, dport]
while len(pkt) > 0 :
if(len(pkt)) > 54:
pkt = sock.recv(2048)
ethHeader = pkt[0][0:14]
ipHeader = pkt[0][14:34]
tcpHeader = pkt[0][34:54]
ethH = struct.unpack("!6s6s2s",ethHeader)
ethdata = processEth(ethH)
ipH = struct.unpack("!12s4s4s",ipHeader)
ipdata = processIP(ipH)
tcpH = struct.unpack("!HH16", tcpHeader)
tcpdata = processTCP(tcpH)
print "S.mac "+ethdata[0]+" D.mac "+ethdata[1]+" from: "+ipdata[0]+":"+tcpdata[0]+" to: "+ipdata[1]+":"+tcpdata[1]
#time.sleep(1);
else:
continue

If you showed all the code, you are running into an endless loop.
Whenever a paket is coming in which has not a length greater then 54 bytes, you end up reading the same packet all the time.
Additionally, socket.recv() returns a string/byte sequence; your approach of accessing the data is wrong. pkt[0] returns a string with length 1; pkt[0][x:y] will not return something useful.
I am not familiar with using sockets, but with some changes I got output that might look similar to what you intended (there is something missing in processEth() I think...).
[...]
while len(pkt) > 0:
print "Waiting.."
pkt = sock.recv(2048)
print "received"
if(len(pkt)) > 54:
ethHeader = pkt[0:14]
ipHeader = pkt[14:34]
tcpHeader = pkt[34:38]
ethH = struct.unpack("!6s6s2s",ethHeader)
ethdata = processEth(ethH)
ipH = struct.unpack("!12s4s4s",ipHeader)
ipdata = processIP(ipH)
tcpH = struct.unpack("!HH16", tcpHeader)
tcpdata = processTCP(tcpH)
print "S.mac "+ethdata[0]+" D.mac "+ethdata[1]+" from: "+ipdata[0]+":"+tcpdata[0]+" to: "+ipdata[1]+":"+tcpdata[1]
#time.sleep(1);
else:
continue