Python 套接字 - struct.error：解包需要 4 字节的缓冲区

Question

我写了一个基本的套接字程序，客户端将图像发送到服务器。

client.py

import socket
from PIL import ImageFile
import struct

ImageFile.LOAD_TRUNCATED_IMAGES = True

HOST = "127.0.0.1"  # The server's hostname or IP address
PORT = 65432  # The port used by the server

img_byte = None
with open('test-images/hummingbird-1.jpeg', 'rb') as fp:
    img_byte = fp.read()

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((HOST, PORT))
    length = len(img_byte)
    s.sendall(struct.pack('!I', length))
    s.sendall(img_byte)

, 和server.py

import socket
import struct


HOST = "127.0.0.1"  # Standard loopback interface address (localhost)
PORT = 65432  # Port to listen on (non-privileged ports are > 1023)

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen()
    conn, addr = s.accept()
    with conn:
        print(f"Connected by {addr}")
        while True:
            buf = conn.recv(4)
            (length, ) = struct.unpack('!I', buf)
            data = b''
            while len(data) < length:
                to_read = length - len(data)
                data += conn.recv(4096 if to_read > 4096 else to_read)
                if not data:
                    break

在服务器端，我收到此错误：

    (length, ) = struct.unpack('!I', buf)
struct.error: unpack requires a buffer of 4 bytes

我想我错过了一些决定性的东西，但我想不通。

Answer 1

根据@Mark Tolonen 的建议，我能够修改并运行server.py ，如下所示：

import socket
import struct


HOST = "127.0.0.1"  # Standard loopback interface address (localhost)
PORT = 65432  # Port to listen on (non-privileged ports are > 1023)

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen()
    conn, addr = s.accept()
    with conn:
        print(f"Connected by {addr}")
        data = b''
        buf = b''
        payload_size = struct.calcsize("!I")
        print("payload_size: {}".format(payload_size))
        while True:
            while len(buf) < payload_size:
                buf += conn.recv(4096)
            length = struct.unpack('!I', buf[:payload_size])[0]
            data = buf[payload_size:]
            while len(data) < length:
                to_read = length - len(data)
                data += conn.recv(4096 if to_read > 4096 else to_read)
                if not data:
                    break
            file = open('rec-images/image.jpeg', 'wb')
            file.write(data)
            file.close()