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()
原文地址：https://www.cnblogs.com/cnlogs1/p/9649145.html
时间： 2024-08-29 13:42:23