table of Contents
Stick package problem
What is the problem then stick package?
When we write tcp socket programming, tcp protocol is a streaming protocol, the data sent by the server for the first time, a one-time client can not accurately received, the next data sent with the last data stick together.
which is:
1, the data size can not predict the length of the other party needs to receive
2, a plurality of successive small amount of data transmitted, and the short time interval of data is transmitted together with a disposable package
TCP protocol features:
Multiple small amounts of data will continuously transmitted, and the short time interval of one-time data transmission is completed
subprocess module
We use the subprocess module to demonstrate a stick package issue.
# 服务端
# coding=utf-8
import socket
import subprocess
server = socket.socket()
address = ("127.0.0.1",8888)
server.bind(address)
server.listen(5)
while True:
conn , addr = server.accept()
while True:
try:
cmd = conn.recv(1024).decode("utf-8")
print(cmd)
if cmd == "q":
break
obj = subprocess.Popen(
cmd,shell=True,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE
)
res = obj.stdout.read() + obj.stderr.read()
conn.send(res)
except Exception:
break
conn.close()# 客户端
# coding=utf-8
import socket
client = socket.socket()
address = ("127.0.0.1",8888)
client.connect(address)
while True:
cmd = input("请输入>>>")
client.send(cmd.encode("utf-8"))
if cmd == "q":
break
data = client.recv(1024)
print(data.decode("gbk"))
client.close()Terminal print results
请输入>>>tasklist
映像名称 PID 会话名 会话# 内存使用
========================= ======== ================ =========== ============
System Idle Process 0 Services 0 24 K
System 4 Services 0 3,172 K
smss.exe 352 Services 0 1,200 K
csrss.exe 464 Services 0 6,656 K
wininit.exe 572 Services 0 5,168 K
csrss.exe 588 Console 1 77,948 K
services.exe 636 Services 0 12,288 K
lsass.exe 652 Services 0 11,164 K
lsm.exe 660 Services 0 4,664 K
winlogon.exe 744 Console 1 8,180 K
svchost.exe 812 Services 0 10,040 K
svchost.
请输入>>>dir
exe 892 Services 0 8,280 K
svchost.exe 980 Services 0 21,744 K
svchost.exe 168 Services 0 21,060 K
svchost.exe 388 Services 0 40,792 K
svchost.exe 908 Services 0 12,252 K
WUDFHost.exe 1100 Services 0 8,096 K
ZhuDongFangYu.exe 1188 Services 0 23,784 K
svchost.exe 1236 Services 0 17,532 K
wlanext.exe 1412 Services 0 5,268 K
conhost.exe 1420 Services 0 2,860 K
dwm.exe 1536 Console 1 38,436 K
explorer.exe 1588 Console 1 70,028 K
spoolsv.exe 1612 Services 0 12,204 K
svchost.exe We saw after the losers tasklist command, enter other command again, or the result of the previous command,
So long proven data server for the first time sent a one-time client can not accurately received, the next data sent with the last data stick together. We received at the client when the data size of 1024 bytes is received, the server receives the execution result exceeds the size of the heap so that the result is equivalent to the back, is transmitted together, it is not the right next Run Results , then we need to solve this problem you need to use struct module
struct module
struct module ,, header must be defined first transmission header, and then transmits the real data
# 服务端
# coding=utf-8
import struct
import socket
import subprocess
server = socket.socket()
address = ("127.0.0.1",8888)
server.bind(address)
server.listen(5)
while True:
conn,addr = server.accept()
while True:
try:
cmd = conn.recv(1024).decode("utf-8")
print(cmd)
if cmd == "q":
break
obj = subprocess.Popen(
cmd ,shell=True,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE
)
res = obj.stdout.read() + obj.stderr.read()
# 将执行结果计算长度用i模式打包
res_len = struct.pack("i",len(res))
# 先发送数据长度
conn.send(res_len)
# 再发送真实数据
conn.send(res)
except Exception:
break
conn.close()# 客户端
# coding=utf-8
import socket
import struct
client = socket.socket()
address = ("127.0.0.1",8888)
client.connect(address)
while True:
cmd = input("请输入命令>>>")
client.send(cmd.encode("utf-8"))
if cmd == "q":
break
# 用struct模块接收的长度统一是4个字节，
head = client.recv(4)
# 然后用struct模块解包得到数据的真实长度，返回的是元组类型，0表示第一个元素，就是真实长度
data_len = struct.unpack("i",head)[0]
# 然后再把真实长度接收即可。
data = client.recv(data_len)
print(data.decode("gbk"))
client.close()UDP protocol programming
A transmission protocol is udp
1) does not need to establish a two-way channel
2) does not stick package
3) The client sends data to the server, the server returns without waiting for the reception success
4) easy to lose data, data insecurity.
TCP: equivalent to the phone
UDP: the equivalent of texting
Easy qq chat room
# 服务端
# coding=utf-8
import socket
server = socket.socket(type=socket.SOCK_DGRAM)
address = ("127.0.0.1",8888)
server.bind(address)
while True:
msg,addr = server.recvfrom(1024)
print(msg.decode("utf-8"))
# 服务端往客户端发送消息
send_msg = input("服务端发送消息")
server.sendto(send_msg.encode("utf-8"),addr)
# 客户端
# coding=utf-8
import socket
client = socket.socket(type=socket.SOCK_DGRAM)
address = ("127.0.0.1",8888)
while True:
send_msg = input("请输入信息")
client.sendto(send_msg.encode("utf-8"),address)
data = client.recv(1024)
print(data.decode("utf-8"))