Python套接字模块：Recv（）数据响应中断
说明
我目前正在尝试使用python脚本控制智能电源板。为此，我正在使用与套接字模块的TCP连接。大约75％的时间，我得到了我正在寻找的响应/数据，一切都很完美。但是，大约25％的时间，响应被切断为完全相同的长度，1024字节。这对我没有任何意义，因为我的缓冲区大小实际设置为2048字节。我在使用recv（）之间等待的速度似乎也没有影响/导致这种情况。Altough TCP是一个字节流，它是否仍然可能与数据包碎片有关？
代码
主要代码
ip='192.168.0.62'
port=9999
sock_tcp = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock_tcp.connect((ip, port))
sock_tcp.send(encrypt('{"system":{"get_sysinfo":{}}}'))
data = sock_tcp.recv(2048)
sock_tcp.close()
print len(data) #On succesful runs output is 1221, on unsuccesful runs it is 1024
rec = decrypt(data[4:])
print str(rec) #See output below
加密功能
def encrypt(string):
key = 171
result = pack('>I', len(string))
for i in string:
a = key ^ ord(i)
key = a
result += chr(a)
return result
解密功能
def decrypt(string):
key = 171
result = ""
for i in string:
a = key ^ ord(i)
key = ord(i)
result += chr(a)
return result
输出
我收到的字符串本身。它最像是不相关的，但我认为无论如何我都会包含它。这是变量rec的值。
期望和定期输出
完全想要的输出
{"system":{"get_sysinfo":{"sw_ver":"1.0.6 Build 180627 Rel.081000","hw_ver":"1.0","model":"HS300(US)","deviceId":"80067B24A755F99C4D6C1807455E09F91AB7B2AA","oemId":"5C9E6254BEBAED63B2B6102966D24C17","hwId":"34C41AA028022D0CCEA5E678E8547C54","rssi":-60,"longitude_i":-1222955,"latitude_i":379078,"alias":"TP-LINK_Power Strip_4F01","mic_type":"IOT.SMARTPLUGSWITCH","feature":"TIM:ENE","mac":"B0:BE:76:12:4F:01","updating":0,"led_off":0,"children":[{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA00","state":0,"alias":"CezHeat","on_time":0,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA01","state":1,"alias":"CezUVB","on_time":191208,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA02","state":1,"alias":"CyanHeat","on_time":191208,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA03","state":1,"alias":"ZanderHeat","on_time":191208,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA04","state":1,"alias":"CairoHeat","on_time":191208,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA05","state":1,"alias":"KodaMister","on_time":191208,"next_action":{"type":-1}}],"child_num":6,"err_code":0}}}
异常输出
{"system":{"get_sysinfo":{"sw_ver":"1.0.6 Build 180627 Rel.081000","hw_ver":"1.0","model":"HS300(US)","deviceId":"80067B24A755F99C4D6C1807455E09F91AB7B2AA","oemId":"5C9E6254BEBAED63B2B6102966D24C17","hwId":"34C41AA028022D0CCEA5E678E8547C54","rssi":-59,"longitude_i":-1222955,"latitude_i":379078,"alias":"TP-LINK_Power Strip_4F01","mic_type":"IOT.SMARTPLUGSWITCH","feature":"TIM:ENE","mac":"B0:BE:76:12:4F:01","updating":0,"led_off":0,"children":[{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA00","state":0,"alias":"CezHeat","on_time":0,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA01","state":1,"alias":"CezUVB","on_time":191207,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA02","state":1,"alias":"CyanHeat","on_time":191207,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA03","state":1,"alias":"ZanderHeat","on_time":191207,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA04","state":1,"alias":"CairoHeat","on
结论
如果有人能够为我提供关于为什么输出/流被切断的解决方案或解释，那将非常感激。我使用了很多来自这个开源模块的代码。我也希望更多地了解这一切是如何运作的，所以如果你能解释一下，我会非常感激。
回答 2
Stack Overflow用户
发布于 2019-04-01 09:17:36
问题的原因确实是TCP是流协议，因此数据包可以在任何状态进行分段或重组：发送方TCP / IP堆栈，网络设备，接收方TCP / IP堆栈 - 我在其中包含用户层库这里为了简化TCP / IP堆栈。
这就是为什么你应该总是在TCP之上使用更高级别的协议才能在合理的消息中分割流。在这里您可以注意到消息的结尾'}}}'，因此您可以在缓冲区中连接输入，直到找到该模式：
def recv_until(c, guard):
"""Receive data from a socket until guard if found on input"""
guard_sz = len(guard) - 1
data = b''
sz = 0
while True:
buffer = c.recv(1024) # read by chuncks of size 1024 (change value to your needs)
got = len(buffer)
data += buffer # concatenate in buffer
ix = data.find(guard, sz - guard_sz if sz > guard_sz else 0) # is guard found?
if ix != -1:
return (data[:ix + guard_sz + 1], # return the message, and what could be behind it
data[ix + guard_sz + 1:])
sz += got
诀窍是考虑来自最后一个块的guard_sz字节，在防护可以分成两个块的情况下。
Stack Overflow用户
发布于 2019-04-01 10:23:54
Marco，请使用recv_into(buffer[, nbytes[, flags]])socket的方法。
我的TCP-microserver示例：
import socket
import struct
def readReliably(s,n):
buf = bytearray(n)
view = memoryview(buf)
sz = s.recv_into(view,n)
return sz,buf
def writeReliably(s,buf,n):
sz = 0
while sz < n:
sz += s.send(buf[sz:],n-sz)
# Client
host = "127.0.0.1"
port = 23456
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(10)
s.connect((host,port))
# Request
buf = struct.pack("4B",*[0x01,0x02,0x03,0x04])
io.writeReliably(s,buf,4)
# Response
sz,buf = io.readReliably(s,4)
a = struct.unpack("4B",buf)
print repr(a)
# Server
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
#s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
#s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
#s.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
s.bind((host,port))
s.listen(10) # unaccepted connections
while True:
sk,skfrom = s.accept()
sz,buf = io.readReliably(sk,4)
a = struct.unpack("4B",buf)
print repr(a)
# ...
io.writeReliably(sk,struct.pack("4B",*[0x01,0x02,0x03,0x04]))
https://stackoverflow.com/questions/-100008998
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