Question

我正在尝试发送一个包含20字节校验和，10字节序列和482字节的文件的数据包。这就是我在下面的内容。如何发送包含所有信息的数据包以及服务器如何知道什么是什么？

import socket
import hashlib

buffer_size = 482
port = 5900
file = open('helloworld.txt', 'rb')
transfer = file.read(buffer_size)
hash_object = hashlib.sha1(transfer)
checksum = hash_object.hexdigest()
addr = ('localhost', port)
sock = socket.socket()
sock.connect(addr)
print('Connected to', addr)
sock.sendto((checksum + transfer))
file.close()
print("File sent")
sock.close()
sock.send()

Answer 1

为TCP数据流定义面向字节的协议。你的“10字节序列”数据没有被证明，所以我会举一个例子来说明。例如：

将传输大小发送为2字节的大端值。
发送传输数据的20字节SHA1摘要。
发送转移数据

示例：

import socket
import hashlib
import struct
import os

buffer_size = 482
port = 8000
transfer = os.urandom(buffer_size) # generate some data
hash_object = hashlib.sha1(transfer)
checksum = hash_object.digest() # digest (not hexdigest) is a 20-byte string.
addr = 'localhost', port
sock = socket.socket()
sock.connect(addr)
print('Connected to', addr)
sock.sendall(struct.pack('>H',buffer_size) + checksum + transfer)
print("File sent")
sock.close()

接收服务器可能如下所示。请注意，TCP是字节流协议，因此阻塞recv(2048)可能返回0（套接字关闭）或1-2048字节。我有目的地为接收选择了一个小的奇数值，以证明你应该根据协议缓冲读取和提取数据。如果数据流提前结束，则此示例无法处理。

import socket
import struct
import hashlib

class Buffer:

    def __init__(self,sock):
        self.sock = sock
        self.buffer = b''

    def get(self,length):
        # Make sure enough bytes to satisfy the length requested
        # are in the buffer.
        while len(self.buffer) < length:
            data = self.sock.recv(7)
            if not data: break
            self.buffer += data
        # Split off from the current buffer the bytes requested.
        # Keep the remainder for the next request.
        rcv,self.buffer = self.buffer[:length],self.buffer[length:]
        return rcv

s = socket.socket()
s.bind(('',8000))
s.listen(1)
c,a = s.accept()
buf = Buffer(c)
length = struct.unpack('>H',buf.get(2))[0]
chksm = buf.get(20)
transfer = buf.get(length)
verify = hashlib.sha1(transfer)
print(chksm == verify.digest())  # should be "True"
c.close()
s.close()

使用文件中的数据发送自定义数据包结构

1 个答案: