Python3 套接字类型错误:必须是 str，而不是字节

Question

下面是使用套接字将图像数据从客户端发送到服务器的代码片段。

虽然代码在Python2上运行没有任何问题，但我在Python3中遇到以下错误

server.py:
===========
import socket
import sys
import cv2
import pickle
import numpy as np
import struct ## new
HOST=''
PORT=8089
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
print('Socket created')
s.bind((HOST,PORT))
print('Socket bind complete')
s.listen(10)
print('Socket now listening')
conn,addr=s.accept()
### new
data = ""
payload_size = struct.calcsize("L") 
while True:
while len(data) < payload_size:
data += conn.recv(4096)
packed_msg_size = data[:payload_size]
data = data[payload_size:]
msg_size = struct.unpack("L", packed_msg_size)[0]
while len(data) < msg_size:
data += conn.recv(4096)
frame_data = data[:msg_size]
data = data[msg_size:]
###
frame=pickle.loads(frame_data)
print(frame)
cv2.imshow('frame',frame)
key = cv2.waitKey(10)
if (key == 27) or (key == 113):
break
# cap.release()
cv2.destroyAllWindows()

Error in server.py:
====================
$ python3 server.py
Socket created
Socket bind complete
Socket now listening
Traceback (most recent call last):
File "server.py", line 26, in <module>
data += conn.recv(4096)
TypeError: must be str, not bytes


client.py:
===========
import cv2
import numpy as np
import socket
import sys
import pickle
import struct ### new code
cap=cv2.VideoCapture(0)
clientsocket=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
clientsocket.connect(('localhost',8089))
while True:
ret,frame=cap.read()
data = pickle.dumps(frame) ### new code
clientsocket.sendall(struct.pack("L", len(data))+data) ### new code

Error in client.py:
===================
$ python3 client.py
Traceback (most recent call last):
File "client.py", line 13, in <module>
clientsocket.sendall(struct.pack("L", len(data))+data) ### new code
BrokenPipeError: [Errno 32] Broken pipe

Answer 1

在将struct.pack("L"， len(data(( 代码分离到 client.py 文件中的新行后，我在Python3上得到了它。

以下是更新的代码：

server.py
=========
import pickle
import socket
import struct
import cv2
HOST = ''
PORT = 8089
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print('Socket created')
s.bind((HOST, PORT))
print('Socket bind complete')
s.listen(10)
print('Socket now listening')
conn, addr = s.accept()
data = b'' ### CHANGED
payload_size = struct.calcsize("L") ### CHANGED
while True:
# Retrieve message size
while len(data) < payload_size:
data += conn.recv(4096)
packed_msg_size = data[:payload_size]
data = data[payload_size:]
msg_size = struct.unpack("L", packed_msg_size)[0] ### CHANGED
# Retrieve all data based on message size
while len(data) < msg_size:
data += conn.recv(4096)
frame_data = data[:msg_size]
data = data[msg_size:]
# Extract frame
frame = pickle.loads(frame_data)
# Display
cv2.imshow('frame', frame)
ch = cv2.waitKey(1)
if ch & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()

client.py
=========
import cv2
import numpy as np
import socket
import sys
import pickle
import struct
cap=cv2.VideoCapture(0)
clientsocket=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
clientsocket.connect(('localhost',8089))
while True:
ret,frame=cap.read()
# Serialize frame
data = pickle.dumps(frame)
# Send message length first
message_size = struct.pack("L", len(data)) ### CHANGED
# Then data
clientsocket.sendall(message_size + data)

cap.release()
cv2.destroyAllWindows()