内容回顾

黏包

  • tcp协议为了保证数据的可靠传输和传输效率
    • 合包机制 : 连续多条短数据会合并成一条
    • 拆包机制 : 一个过大的数据会在发出之前被拆成几个小包
  • tcp的黏包发生在两端:
    • 发送端 : 合包机制导致
    • 接收端 : 接收不及时
  • 发生黏包的本质:由于tcp协议流式传输的特点导致数据与数据之间边界不清晰
  • 自定义协议
    • struct:能够把一个任意的数字变成固定的四个字节
    • 基础版本 :先发送数据的长度(固定4字节),再发送数据本身
    • 进阶版本 :先发送字典的长度(固定4字节),再发送字典,再发送数据本身

总结

  • 很多概念
    • osi五层协议
      tcp协议和udp协议
    • tcp协议 三次握手 四次挥手
    • 代码
    • 区别
      • tcp 面向连接,流式传输,慢,可靠,全双工
      • udp 面向数据包,快,不可靠,无连接
  • tcp协议 黏包
    • 自定义协议来解决问题 struct
    • 为什么会发生黏包
  • tcp协议能够处理多个client的请求 - socketserver
  • 验证客户端合法性 hmac/hashilib

课上代码

并发的socketserver

Server

import time
import socketserver

class Myserver(socketserver.BaseRequestHandler):
    def handle(self):
        conn = self.request
        for i in range(200):
            conn.send(('hello%s'%i).encode('utf-8'))
            print(conn.recv(1024))
            time.sleep(0.5)


server = socketserver.ThreadingTCPServer(('127.0.0.1',9001),Myserver)
server.serve_forever()

ClientI

import socket

sk = socket.socket()
sk.connect(('127.0.0.1',9001))
while True:
    msg = sk.recv(1024)
    print(msg)
    sk.send(b'byebye')
sk.close()

ClientII

import socket

sk = socket.socket()
sk.connect(('127.0.0.1',9001))
while True:
    msg = sk.recv(1024)
    print(msg)
    sk.send(b'byebye')
sk.close()

验证客户端的合法性

  • 不是一个面向用户的 需要用户自己输入用户名和密码的
  • 而是面向一台server的所有的(500台)客户端
  • 都以一种我们共同的方式来进行一个验证

Server

import os
import hashlib
import socket

secret_key = b'alex sb'
#os.urandom(32) 给每一客户端发送一个随机的字符串,来保证即使数据被拦截你也不能使用这个消息
sk = socket.socket()
sk.bind(('127.0.0.1',9001))
sk.listen()

conn,addr = sk.accept()
rand = os.urandom(32)
conn.send(rand)

sha = hashlib.sha1(secret_key)
sha.update(rand)
res = sha.hexdigest()

ret = conn.recv(1024).decode('utf-8')
if ret == res:
    print('是合法的客户端')
else:
    print('不是合法的客户端')
    conn.close()

Client

import socket
import hashlib

secret_key = b'alexsb'
sk = socket.socket()
sk.connect(('127.0.0.1',9001))

rand = sk.recv(32)

sha = hashlib.sha1(secret_key)
sha.update(rand)
res = sha.hexdigest()

sk.send(res.encode('utf-8'))

sk.close()

hmac

import os
import hmac

hmac = hmac.new(b'alex sb',os.urandom(32))
print(hmac.digest())

验证客户端的合法性_hmac

Server

import os
import hmac
import socket

secret_key = b'alex sb'
#os.urandom(32) 给每一客户端发送一个随机的字符串,来保证即使数据被拦截你也不能使用这个消息
sk = socket.socket()
sk.bind(('127.0.0.1',9001))
sk.listen()

conn,addr = sk.accept()
rand = os.urandom(32)
conn.send(rand)

hmac = hmac.new(secret_key,rand)
res = hmac.digest()

ret = conn.recv(1024)
if ret == res:
    print('是合法的客户端')
else:
    print('不是合法的客户端')
    conn.close()

Client

import hmac
import socket


secret_key = b'alex sb'
sk = socket.socket()
sk.connect(('127.0.0.1',9001))

rand = sk.recv(32)

hmac = hmac.new(secret_key,rand)
res = hmac.digest()

sk.send(res)

sk.close()

作业_大文件的传输

Server

import json
import struct
import socket

sk = socket.socket()
sk.bind(('127.0.0.1',9001))
sk.listen()

conn,addr = sk.accept()
len_bytes = conn.recv(4)
num = struct.unpack('i',len_bytes)[0]
str_dic = conn.recv(num).decode('utf-8')
dic = json.loads(str_dic)

with open(dic['filename'],'wb') as f:
    while dic['filesize']:
        content = conn.recv(2048)
        f.write(content)
        dic['filesize'] -= len(content)

Client

import os
import json
import struct
import socket

sk = socket.socket()
sk.connect(('127.0.0.1',9001))

file_path = input('>>>')
filename = os.path.basename(file_path)
filesize = os.path.getsize(file_path)
dic = {'filename':filename,'filesize':filesize}
bytes_dic = json.dumps(dic).encode('utf-8')

len_bytes = struct.pack('i',len(bytes_dic))
sk.send(len_bytes)
sk.send(bytes_dic)

with open(file_path,'rb') as f:
    while filesize > 2048:
        content = f.read(2048)
        sk.send(content)
        filesize -= 2048
    else:
        content = f.read()
        sk.send(content)

sk.close()
# 175,060,348
# 152,117,248

作业_认证+上传

Server

import json
import socket
import struct
import hashlib
def get_md5(usr,pwd):
    md5 = hashlib.md5(usr.encode('utf-8'))
    md5.update(pwd.encode('utf-8'))
    return md5.hexdigest()

def login(conn):
    msg = conn.recv(1024).decode('utf-8')
    dic = json.loads(msg)
    with open('userinfo', encoding='utf-8') as f:
        for line in f:
            username, password = line.strip().split('|')
            if username == dic['user'] and password == get_md5(dic['user'], dic['passwd']):
                res = json.dumps({'flag': True}).encode('utf-8')
                conn.send(res)
                return True
        else:
            res = json.dumps({'flag': False}).encode('utf-8')
            conn.send(res)
            return False

def upload(conn):
    len_bytes = conn.recv(4)
    num = struct.unpack('i', len_bytes)[0]
    str_dic = conn.recv(num).decode('utf-8')
    dic = json.loads(str_dic)

    with open(dic['filename'], 'wb') as f:
        while dic['filesize']:
            content = conn.recv(2048)
            f.write(content)
            dic['filesize'] -= len(content)

sk = socket.socket()
sk.bind(('127.0.0.1',9001))
sk.listen()
while True:
    try:
        conn,addr = sk.accept()
        ret = login(conn)
        if ret:
            upload(conn)
    except Exception as e:
        print(e)
    finally:
        conn.close()
sk.close()

Client

import os
import json
import socket
import struct

def upload(sk):
    # 上传文件
    file_path = input('>>>')
    filename = os.path.basename(file_path)
    filesize = os.path.getsize(file_path)
    dic = {'filename': filename, 'filesize': filesize}
    bytes_dic = json.dumps(dic).encode('utf-8')

    len_bytes = struct.pack('i', len(bytes_dic))
    sk.send(len_bytes)
    sk.send(bytes_dic)

    with open(file_path, 'rb') as f:
        while filesize > 2048:
            content = f.read(2048)
            sk.send(content)
            filesize -= 2048
        else:
            content = f.read()
            sk.send(content)

usr = input('username :')
pwd = input('password :')
dic = {'operate':'login','user':usr,'passwd':pwd}
bytes_dic = json.dumps(dic).encode('utf-8')

sk = socket.socket()
sk.connect(('127.0.0.1',9001))
sk.send(bytes_dic)

res = sk.recv(1024).decode('utf-8')
dic = json.loads(res)

if dic['flag']:
    print('登录成功')
    upload(sk)
else:
    print('登录失败')

sk.close()

ClientII

import os
import json
import socket
import struct

def upload(sk):
    # 上传文件
    file_path = input('>>>')
    filename = os.path.basename(file_path)
    filesize = os.path.getsize(file_path)
    dic = {'filename': filename, 'filesize': filesize}
    bytes_dic = json.dumps(dic).encode('utf-8')

    len_bytes = struct.pack('i', len(bytes_dic))
    sk.send(len_bytes)
    sk.send(bytes_dic)

    with open(file_path, 'rb') as f:
        while filesize > 2048:
            content = f.read(2048)
            sk.send(content)
            filesize -= 2048
        else:
            content = f.read()
            sk.send(content)

usr = input('username :')
pwd = input('password :')
dic = {'operate':'login','user':usr,'passwd':pwd}
bytes_dic = json.dumps(dic).encode('utf-8')
sk = socket.socket()
sk.connect(('127.0.0.1',9001))
sk.send(bytes_dic)

res = sk.recv(1024).decode('utf-8')
dic = json.loads(res)
if dic['flag']:
    print('登录成功')
    upload(sk)
else:
    print('登录失败')

sk.close()
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