[英]Python : Socket Sending Struct(having C stuct as Example)
下面是C語言的結構,我嘗試轉換為Python,並使用Socket發送結構
C:
struct CommandReq
{
char sMark[6]; //start flag\r\n*KW
short nPackLen; //packet length
short nFlag; //command ID 0x0002
int nGisIp; //GIS port
short nPort; //GIS Port
char sData[50]; //command string
char sEnd[2]; //end flag "\r\n"
};
//source code
CommandReq stResq;
memset(&stResq, 0, sizeof(stResq));
sprintf(stResq.sMark, "\r\n%s", "*KW");
stResq.nFlag = 0x0002;
stResq.nPackLen = sizeof(stResq);
stResq.nGisIp = 0;
stResq.nPort = 0;
strcpy(stResq.sData, "*KW,CC09C00001,015,080756,#");
strncpy(stResq.sEnd, "\r\n", 2);
我使用namedtuple創建了Python結構,並使用套接字發送了該結構。 但不幸的是失敗了。
蟒蛇:
from collections import namedtuple
MyStruct = namedtuple("MyStruct", "sMark nPackLen nFlag nGisIp nPort sData sEnd")
弄清楚之后,必須在python 3.x中添加字符串.encode(“ ascii”)
format_ = "6shhih50s2s"
MyStruct = namedtuple("MyStruct", "sMark nPackLen nFlag nGisIp nPort sData sEnd")
tuple_to_send = MyStruct(sMark="\r\n{}".format("*KW").encode("ascii"),
nPackLen=struct.calcsize(format_),
nFlag=0x0002,
nGisIp=0,
nPort=0,
sData= "*KW,NR09G05133,015,080756,#".encode("ascii"),
sEnd="\r\n".encode("ascii"))
string_to_send = struct.pack(format_, *tuple_to_send._asdict().values()
socket.sendto(string_to_send, self.client_address)
下面是數據包與結構發送
format_ = "6shhih50s2s" //total bytes should be 68 bytes?
0d0a2a4b5700 //6 char \r\n*KW
4600 // packet length 70 bytes
0200 //command ID 0x0002,short 2 bytes
00000000 //GIS port is integer 4 bytes
0000 //GIS Port short 2 bytes
0000 //unknown??what is this?
2a4b572c4e5230394730353133332c3031352c3038303735362c230000000000000000000000000000000000000000000000 //sData[50] char 50 bytes
0d0a //sEnd 2 char,2 bytes
2個未知字節怎么來?
namedtuple不能真正與c結構媲美。 如果您習慣使用結構,可以查看struct
-module來將結構化信息轉換為字符串。
通常,Pythonistas傾向於使用pickle
-module進行序列化。
from collections import namedtuple
import pickle # or cPickle, it's faster
MyStruct = namedtuple("MyStruct", "sMark nPackLen nFlag nGisIp nPort sData sEnd")
tuple_to_send = MyStruct(sMark="abcdef", nPackLen=...)
string_to_send = pickle.dumps(tuple_to_send)
泡菜有兩種口味, pickle
和cPickle
。 后者更快,但是僅在CPython中可用(大多數程序員使用),而pickle在Jython,IronPython等中也可用。
如果您想堅持使用struct(例如,因為另一端希望使用這種格式),則格式字符串將為
format_ = "6shhih50s2s"
因此,您可以執行以下操作:
import struct
from collections import namedtuple
format_ = "6shhih50s2s"
MyStruct = namedtuple("MyStruct", "sMark nPackLen nFlag nGisIp nPort sData sEnd")
tuple_to_send = MyStruct(sMark="\r\n{}".format("*KW"),
nPackLen=struct.calcsize(format_),
nFlag=0x0002,
nGisIp=0,
nPort=0,
sData= "*KW,NR09G05133,015,080756,#",
sEnd="\r\n")
string_to_send = struct.pack(format_, *tuple_to_send._asdict().values())
順便說一句:namedtuple是不可變的,即您不能做
tuple_to_send.sMark = "bcdefg"
更改一些屬性。 如果需要這種行為,則必須創建一個類。
編輯
對於Python 3,字符串處理已更改。 必須執行從Unicode到字節的轉換,例如
import struct
from collections import namedtuple
format_ = "6shhih50s2s"
MyStruct = namedtuple("MyStruct", "sMark nPackLen nFlag nGisIp nPort sData sEnd")
tuple_to_send = MyStruct(sMark="\r\n{}".format("*KW").encode("ascii"),
nPackLen=struct.calcsize(format_),
nFlag=0x0002,
nGisIp=0,
nPort=0,
sData= "*KW,NR09G05133,015,080756,#".encode("ascii"),
sEnd=b"\r\n")
string_to_send = struct.pack(format_, *tuple_to_send._asdict().values())
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