第六章 网络编程-SOCKET开发——续2

6.5——粘包现象与解决方案

简单远程执行命令程序开发

是时候用户socket干点正事呀，我们来写一个远程执行命令的程序，写一个socket client端在windows端发送指令，一个socket server在Linux端执行命令并返回结果给客户端

执行命令的话，肯定是用我们学过的subprocess模块啦，但注意注意注意：

res=subprocess.Popen(cmd.deocde('utf-8'),shell=subprocess.PIPE,stdout=subprocess.PIPE

命令结果的编码是以当前所在的系统为准的，如果是windows，那么res.stdout.read()读出的就是GBK编码的，在接收端需要用GBK解码，且只能从管道里读一次结果

ssh server

import socket
import subprocess

ip_port = ('127.0.0.1', 8080)


tcp_socket_server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcp_socket_server.bind(ip_port)
tcp_socket_server.listen(5)

while True:
    conn, addr = tcp_socket_server.accept()
    print('客户端', addr)

    while True:
        cmd = conn.recv(1024)
        if len(cmd) == 0: break
        print("recv cmd",cmd)
        res = subprocess.Popen(cmd.decode('utf-8'), shell=True,
                               stdout=subprocess.PIPE,
                               stdin=subprocess.PIPE,
                               stderr=subprocess.PIPE)

        stderr = res.stderr.read()
        stdout = res.stdout.read()
        print("res length",len(stdout))
        conn.send(stderr)
        conn.send(stdout)

ssh client

import socket
ip_port = ('127.0.0.1', 8080)

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
res = s.connect_ex(ip_port)

while True:
    msg = input('>>: ').strip()
    if len(msg) == 0: continue
    if msg == 'quit': break

    s.send(msg.encode('utf-8'))
    act_res = s.recv(1024)

    print(act_res.decode('utf-8'), end='')

粘包的解决办法

问题的根源在于，接收端不知道发送端将要传送的字节流的长度，所以解决粘包的方法就是围绕，如何让发送端在发送数据前，把自己将要发送的字节流总大小让接收端知晓，然后接收端来一个死循环接收完所有数据

普通版

服务器端

import socket,subprocess
ip_port=('127.0.0.1',8080)
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

s.bind(ip_port)
s.listen(5)

while True:
    conn,addr=s.accept()
    print('客户端',addr)
    while True:
        msg=conn.recv(1024)
        if not msg:break
        res=subprocess.Popen(msg.decode('utf-8'),shell=True,
                            stdin=subprocess.PIPE,
                         stderr=subprocess.PIPE,
                         stdout=subprocess.PIPE)
        err=res.stderr.read()
        if err:
            ret=err
        else:
            ret=res.stdout.read()
        data_length=len(ret)
        conn.send(str(data_length).encode('utf-8'))
        data=conn.recv(1024).decode('utf-8')
        if data == 'recv_ready':
            conn.sendall(ret)
    conn.close()

客户端

import socket,time
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
res=s.connect_ex(('127.0.0.1',8080))

while True:
    msg=input('>>: ').strip()
    if len(msg) == 0:continue
    if msg == 'quit':break

    s.send(msg.encode('utf-8'))
    length=int(s.recv(1024).decode('utf-8'))
    s.send('recv_ready'.encode('utf-8'))
    send_size=0
    recv_size=0
    data=b''
    while recv_size < length:
        data+=s.recv(1024)
        recv_size+=len(data) #为什么不直接写1024？


    print(data.decode('utf-8'))

为何low？

程序的运行速度远快于网络传输速度，所以在发送一段字节前，先用send去发送该字节流长度，这种方式会放大网络延迟带来的性能损耗

刚才上面 在发送消息之前需先发送消息长度给对端，还必须要等对端返回一个ready收消息的确认，不等到对端确认就直接发消息的话，还是会产生粘包问题(承载消息长度的那条消息和消息本身粘在一起)。 有没有优化的好办法么？

文艺版

思考一个问题，为什么不能在发送了消息长度(称为消息头head吧)给对端后，立刻发消息内容(称为body吧)，是因为怕head 和body 粘在一起，所以通过等对端返回确认来把两条消息中断开。

可不可以直接发head + body,但又能让对端区分出哪个是head，哪个是body呢？我靠、我靠，感觉智商要涨了。

想到了，把head设置成定长的呀，这样对端只要收消息时，先固定收定长的数据，head里写好，后面还有多少是属于这条消息的数据，然后直接写个循环收下来不就完了嘛！唉呀妈呀，我真机智。

可是、可是如何制作定长的消息头呢？假设你有2条消息要发送，第一条消息长度是 3000个字节，第2条消息是200字节。如果消息头只包含消息长度的话，那两个消息的消息头分别是

len(msf1)=4000=4字节
len(msg2)=200=3字节

你的服务端如何完整的收到这个消息头呢？是recv(3)还是recv(4)服务器端怎么知道？用尽我所有知识，我只能想到拼接字符串的办法了，打比方就是设置消息头固定100字节长，不够的拿空字符串去拼接。

server

import socket,json
import subprocess

ip_port = ('127.0.0.1', 8080)

tcp_socket_server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcp_socket_server.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1) #一行代码搞定，写在bind之前
tcp_socket_server.bind(ip_port)
tcp_socket_server.listen(5)

def pack_msg_header(header,size):
    bytes_header = bytes(json.dumps(header),encoding="utf-8")
    fill_up_size = size -  len(bytes_header)
    print("need to fill up ",fill_up_size)

    header['fill'] = header['fill'].zfill(fill_up_size)
    print("new header",header)
    bytes_new_header = bytes(bytes(json.dumps(header),encoding="utf-8"))
    return bytes_new_header

while True:
    conn, addr = tcp_socket_server.accept()
    print('客户端', addr)

    while True:
        cmd = conn.recv(1024)
        if len(cmd) == 0: break
        print("recv cmd",cmd)
        res = subprocess.Popen(cmd.decode('utf-8'), shell=True,
                               stdout=subprocess.PIPE,
                               stdin=subprocess.PIPE,
                               stderr=subprocess.PIPE)

        stderr = res.stderr.read()
        stdout = res.stdout.read()
        print("res length",len(stdout))

        msg_header = {
            'length':len(stdout + stderr),
            'fill':''
        }
        packed_header = pack_msg_header(msg_header,100)
        print("packed header size",packed_header,len(packed_header))
        conn.send(packed_header)
        conn.send(stdout + stderr)

client

import socket
import json

ip_port = ('127.0.0.1', 8080)

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
res = s.connect_ex(ip_port)

while True:
    msg = input('>>: ').strip()
    if len(msg) == 0: continue
    if msg == 'quit': break

    s.send(msg.encode('utf-8'))
    response_msg_header = s.recv(100).decode("utf-8")

    response_msg_header_data = json.loads(response_msg_header)
    msg_size = response_msg_header_data['length']

    res = s.recv(msg_size)
    print("received res size ",len(res))
    print(res.decode('utf-8'), end='')

文艺版二

为字节流加上自定义固定长度报头也可以借助第三方模块struct，用法为

import json,struct
#假设通过客户端上传1T:1073741824000的文件a.txt

#为避免粘包,必须自定制报头
header={'file_size':1073741824000,'file_name':'/a/b/c/d/e/a.txt','md5':'8f6fbf8347faa4924a76856701edb0f3'} #1T数据,文件路径和md5值

#为了该报头能传送,需要序列化并且转为bytes
head_bytes=bytes(json.dumps(header),encoding='utf-8') #序列化并转成bytes,用于传输

#为了让客户端知道报头的长度,用struck将报头长度这个数字转成固定长度:4个字节
head_len_bytes=struct.pack('i',len(head_bytes)) #这4个字节里只包含了一个数字,该数字是报头的长度

#客户端开始发送
conn.send(head_len_bytes) #先发报头的长度,4个bytes
conn.send(head_bytes) #再发报头的字节格式
conn.sendall(文件内容) #然后发真实内容的字节格式

#服务端开始接收
head_len_bytes=s.recv(4) #先收报头4个bytes,得到报头长度的字节格式
x=struct.unpack('i',head_len_bytes)[0] #提取报头的长度

head_bytes=s.recv(x) #按照报头长度x,收取报头的bytes格式
header=json.loads(json.dumps(header)) #提取报头

#最后根据报头的内容提取真实的数据,比如
real_data_len=s.recv(header['file_size'])
s.recv(real_data_len)

使用struct模块实现方式如下

server

import socket,struct,json
import subprocess
phone=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
phone.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1) #就是它，在bind前加

phone.bind(('127.0.0.1',8080))

phone.listen(5)

while True:
    conn,addr=phone.accept()
    while True:
        cmd=conn.recv(1024)
        if not cmd:break
        print('cmd: %s' %cmd)

        res=subprocess.Popen(cmd.decode('utf-8'),
                             shell=True,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
        err=res.stderr.read()
        print(err)
        if err:
            back_msg=err
        else:
            back_msg=res.stdout.read()

        headers={'data_size':len(back_msg)}
        head_json=json.dumps(headers)
        head_json_bytes=bytes(head_json,encoding='utf-8')

        conn.send(struct.pack('i',len(head_json_bytes))) #先发报头的长度
        conn.send(head_json_bytes) #再发报头
        conn.sendall(back_msg) #在发真实的内容

    conn.close()

client

from socket import *
import struct,json

ip_port=('127.0.0.1',8080)
client=socket(AF_INET,SOCK_STREAM)
client.connect(ip_port)

while True:
    cmd=input('>>: ')
    if not cmd:continue
    client.send(bytes(cmd,encoding='utf-8'))

    head=client.recv(4) #先收4个bytes，这里4个bytes里包含了报头的长度
    head_json_len=struct.unpack('i',head)[0] #解出报头的长度
    head_json=json.loads(client.recv(head_json_len).decode('utf-8')) #拿到报头
    data_len=head_json['data_size'] #取出报头内包含的信息

    #开始收数据
    recv_size=0
    recv_data=b''
    while recv_size < data_len:
        recv_data+=client.recv(1024)
        recv_size+=len(recv_data)

    print(recv_data.decode('utf-8'))

6.6——通过socket发送文件

通过socket收发文件软件开发

1、客户端提交命令


2、服务端接收命令，解析，执行下载文件的方法，即以读的方式打开文件，for循环读出文件的一行行内容，然后send给客户端


3、客户端以写的方式打开文件，将接收的内容写入文件中

参照上一小节文艺青年实现版二，示范代码如下

服务端实现

import socket
import struct
import json
import subprocess
import os

class MYTCPServer:
    address_family = socket.AF_INET

    socket_type = socket.SOCK_STREAM

    allow_reuse_address = False

    max_packet_size = 8192

    coding='utf-8'

    request_queue_size = 5

    server_dir='file_upload'

    def __init__(self, server_address, bind_and_activate=True):
        """Constructor.  May be extended, do not override."""
        self.server_address=server_address
        self.socket = socket.socket(self.address_family,
                                    self.socket_type)
        if bind_and_activate:
            try:
                self.server_bind()
                self.server_activate()
            except:
                self.server_close()
                raise

    def server_bind(self):
        """Called by constructor to bind the socket.
        """
        if self.allow_reuse_address:
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.socket.bind(self.server_address)
        self.server_address = self.socket.getsockname()

    def server_activate(self):
        """Called by constructor to activate the server.
        """
        self.socket.listen(self.request_queue_size)

    def server_close(self):
        """Called to clean-up the server.
        """
        self.socket.close()

    def get_request(self):
        """Get the request and client address from the socket.
        """
        return self.socket.accept()

    def close_request(self, request):
        """Called to clean up an individual request."""
        request.close()

    def run(self):
        while True:
            self.conn,self.client_addr=self.get_request()
            print('from client ',self.client_addr)
            while True:
                try:
                    head_struct = self.conn.recv(4)
                    if not head_struct:break

                    head_len = struct.unpack('i', head_struct)[0]
                    head_json = self.conn.recv(head_len).decode(self.coding)
                    head_dic = json.loads(head_json)

                    print(head_dic)
                    #head_dic={'cmd':'put','filename':'a.txt','filesize':123123}
                    cmd=head_dic['cmd']
                    if hasattr(self,cmd):
                        func=getattr(self,cmd)
                        func(head_dic)
                except Exception:
                    break

    def put(self,args):
        file_path=os.path.normpath(os.path.join(
            self.server_dir,
            args['filename']
        ))

        filesize=args['filesize']
        recv_size=0
        print('----->',file_path)
        with open(file_path,'wb') as f:
            while recv_size < filesize:
                recv_data=self.conn.recv(self.max_packet_size)
                f.write(recv_data)
                recv_size+=len(recv_data)
                print('recvsize:%s filesize:%s' %(recv_size,filesize))


tcpserver1=MYTCPServer(('127.0.0.1',8080))

tcpserver1.run()

客户端

import socket
import struct
import json
import os



class MYTCPClient:
    address_family = socket.AF_INET

    socket_type = socket.SOCK_STREAM

    allow_reuse_address = False

    max_packet_size = 8192

    coding='utf-8'

    request_queue_size = 5

    def __init__(self, server_address, connect=True):
        self.server_address=server_address
        self.socket = socket.socket(self.address_family,
                                    self.socket_type)
        if connect:
            try:
                self.client_connect()
            except:
                self.client_close()
                raise

    def client_connect(self):
        self.socket.connect(self.server_address)

    def client_close(self):
        self.socket.close()

    def run(self):
        while True:
            inp=input(">>: ").strip()
            if not inp:continue
            l=inp.split()
            cmd=l[0]
            if hasattr(self,cmd):
                func=getattr(self,cmd)
                func(l)


    def put(self,args):
        cmd=args[0]
        filename=args[1]
        if not os.path.isfile(filename):
            print('file:%s is not exists' %filename)
            return
        else:
            filesize=os.path.getsize(filename)

        head_dic={'cmd':cmd,'filename':os.path.basename(filename),'filesize':filesize}
        print(head_dic)
        head_json=json.dumps(head_dic)
        head_json_bytes=bytes(head_json,encoding=self.coding)

        head_struct=struct.pack('i',len(head_json_bytes))
        self.socket.send(head_struct)
        self.socket.send(head_json_bytes)
        send_size=0
        with open(filename,'rb') as f:
            for line in f:
                self.socket.send(line)
                send_size+=len(line)
                print(send_size)
            else:
                print('upload successful')




client=MYTCPClient(('127.0.0.1',8080))

client.run()