发送图像时出现 Python 套接字错误。无法解码字节/意外的EOF

Question

我正在使用python套接字将图像从笔记本电脑的相机(客户端(传输到树莓pi(服务器(。事情是这样的，我连接到插座，然后我的客户等待信号以便拍照。当信号(来自我的服务器(发送时，我的客户端会拍一张照片，并按顺序发送以下数据；首先，表示图片大小的数字的长度(例如，对于10000个字节，数字为5，对于100000个字节，数量为6，依此类推(，然后发送实际大小，最后将照片作为字节串发送。该过程重复无限次

客户端.py

import cv2
import socket
import os
def send_msg(s, msg):
s.sendall(msg)

s = socket.socket()
port = 24999
ip = '192.168.1.3'
s.connect((ip, port))
video = cv2.VideoCapture(0)
s.recv(1) #Wait until data is sent
while True:
_, img = video.read()
img = cv2.resize(img, (0,0), fx = 0.4, fy = 0.4) #reduce image size
cv2.imwrite("test.jpg", img) #save img
size = os.path.getsize("test.jpg") #get image size
img_str = cv2.imencode('.jpg', img)[1].tostring() #convert to bytes string
sizenum = str(len(str(size))) #how many digits the image size contains
send_msg(s, sizenum.encode())
send_msg(s, str(size).encode('utf-8')) #send actual image size
send_msg(s, img_str) #finally send the image
s.recv(1) #Wait until data is sent

服务器.py

import socket
import ast
def send_msg(client, msg):
client.sendall(msg+b'rn')
def recvall(sock, n):
# Helper function to recv n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
def take_photo(cl):
#RECEIVE LENGTH OF SIZE
while True:
lensize = cl.recv(1)
lensize = lensize.decode('utf-8')
if lensize != "":
break
print("Size is a",lensize,"-digit number")
lensize = lensize.replace("n","").replace(" ","").replace("r","")
#RECEIVE SIZE
size_pic = recvall(cl,ast.literal_eval(lensize)).decode('utf-8')
size_pic = size_pic.replace("n","").replace(" ","").replace("r","")
print("Exact size is",size_pic)
#RECEIVE PHOTO
return lensize,size_pic,bytearray(recvall(cl,ast.literal_eval(size_pic)))
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(("192.168.1.3",24999))
s.listen(1)
while True:
cl_image, addr = s.accept()
break
while True:
try:
send_msg(cl_image, b"1") #Send signal
size1, size2, photo = take_photo(cl_image)
print(photo)
except KeyboardInterrupt:
print("error")
s.close()

问题运行服务器时，在运行几秒钟后出现问题(有时在引发任何异常前仅运行1秒，有时运行5秒或更长时间(

示例运行1(服务器(

Size is a 5 -digit number
Exact size is 21263
7294 from 21263 Not all bytes were read
18974 from 21263 Not all bytes were read
Size is a 5 -digit number
Exact size is 21226
2915 from 21226 Not all bytes were read
4375 from 21226 Not all bytes were read
11675 from 21226 Not all bytes were read
18975 from 21226 Not all bytes were read
Size is a 5 -digit number
Exact size is 21412
2915 from 21412 Not all bytes were read
7295 from 21412 Not all bytes were read
14595 from 21412 Not all bytes were read
Size is a . -digit number
Traceback (most recent call last):
File "sending_test.py", line 46, in <module>
size1, size2, photo = take_photo(cl_image)
File "sending_test.py", line 27, in take_photo
size_pic = recvall(cl,ast.literal_eval(lensize)).decode('utf-8')
File "/usr/lib/python3.7/ast.py", line 46, in literal_eval
node_or_string = parse(node_or_string, mode='eval')
File "/usr/lib/python3.7/ast.py", line 35, in parse
return compile(source, filename, mode, PyCF_ONLY_AST)
File "<unknown>", line 1
.

示例运行2(服务器(

Size is a 5 -digit number
Exact size is 20653
7294 from 20653 Not all bytes were read
14594 from 20653 Not all bytes were read
18974 from 20653 Not all bytes were read
Size is a 5 -digit number
Exact size is 20595
2915 from 20595 Not all bytes were read
8755 from 20595 Not all bytes were read
10215 from 20595 Not all bytes were read
18975 from 20595 Not all bytes were read
Traceback (most recent call last):
File "sending_test.py", line 46, in <module>
size1, size2, photo = take_photo(cl_image)
File "sending_test.py", line 21, in take_photo
lensize = lensize.decode('utf-8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte

我还在服务器的循环中插入了一个print(photo(命令，看看发生了什么，结果就是这样(与其他行相比，见最后一行(

Size is a 3 -digit number
Exact size is 828
bytearray(b'xffxd8xff.......xffxd9')
Size is a 3 -digit number
Exact size is 831
bytearray(b'xffxd8xff......xffxd9')
Size is a 3 -digit number
Exact size is 831
bytearray(b'xffxd8xff.......xffxd9383')

这意味着它读取了更多的(3(个字节(因为3表示大小长度，83来自图像大小，这有点像(83x(

Answer 1

根据评论，我做了一些更改，如下所示：

• 我只是将JPEG编码到内存缓冲区，获取其大小并发送给

• 与其发送一个字符串来表示第二个字符串中的字节数，不如发送一个4字节的网络顺序整数的字节数。让生活更轻松

它在我的机器上似乎工作得很可靠。

这是客户：

#!/usr/bin/env python3
import cv2
import socket
import os
import struct
ip, port = '192.168.0.8', 24999
s = socket.socket()
s.connect((ip, port))
# Start video reader
video = cv2.VideoCapture(0)
while True:
# Wait till data requested, as indicated by receipt of single byte
s.recv(1)
print('CLIENT: Image requested')
# Read a frame of video and reduce size
_, img = video.read()
img = cv2.resize(img, (0,0), fx = 0.4, fy = 0.4)
# JPEG-encode into memory buffer and get size
_, buffer = cv2.imencode('.jpg', img)
nBytes = buffer.size
print(f'CLIENT: nBytes={nBytes}')
# Send 4-byte network order frame size and image
hdr = struct.pack('!i',nBytes)
s.sendall(hdr)
s.sendall(buffer)

这是服务器：

#!/usr/bin/env python3
import time
import socket
import struct
def recvall(sock, n):
# Helper function to recv n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data
def take_photo(cl):
# Get header with number of bytes
header = cl.recv(4)
nBytes = struct.unpack('!i',header)[0]
# Receive actual image
img = recvall(cl, nBytes)
return img
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(("192.168.0.8",24999))
s.listen(1)
while True:
cl_image, addr = s.accept()
break
while True:
try:
# Request image by sending a single byte
cl_image.sendall(b'1')
photo = take_photo(cl_image)
time.sleep(1)
print(f'SERVER: photo received, {len(photo)} bytes')
except KeyboardInterrupt:
print("error")
s.close()

关键字：TCP套接字、流、基于流、基于数据流、消息、基于消息、成帧协议、成帧、htonl、网络顺序、数据包、素数。