Python solves sticky packet phenomenon (struct module)

A. struct module

The module can convert a type to a fixed-length bytes

Import Structlst   = [1,2,4,3,5,]lst1  = [1,2,4,3,5,7,8,9= struct.pack ('i', Len (LST)) # Convert the length of the list to a fixed 4 byte b = Struct.pack('i', Len (lst1))Print  (A,len (a))print(B,len (b))

The type of the symbol and the length table after the conversion:

The struct module implements large file transfers:

#Server SideImportSocketImportstructImportJSONImportOssk=socket.socket () Sk.bind ('127.0.0.1', 8989) ) Sk.listen () conn,addr=sk.accept () len_dic= Struct.unpack ('I', CONN.RECV (4)) [0]#unpack accepts a tuple type, with an index of 0 being the length of the dictionaryStr_dic = Conn.recv (len_dic). Decode ('Utf-8')#To receive a dictionary as a string type based on the length of the dictionaryDIC = Json.loads (str_dic)#converts a dictionary of string types to a dictionary (dict)ifdic['opt'] =='Upload': Up_load='D:\a\b\c\\'+ Os.path.basename (dic['filename'])#Path Stitching    #up_load = os.path.join (' D:\a\b\c\\ ', os.path.basename (dic[' filename '))     whiledic['filesize'] >0:read_size= CONN.RECV (2048) with open (Os.path.abspath (up_load), mode='AB') as F1:f1.write (read_size) dic['filesize'] -=Len (read_size)ifdic['opt'] =='Download': Down_load='D:\a\b\c'conn.send (Json.dumps (Os.listdir (Down_load)). Encode ('Utf-8'))     while1: S= CONN.RECV (2048). Decode ('Utf-8') file= Os.path.abspath (down_load+'/'+s)Print(file)ifos.path.isdir (file): Dic1= {'Tybe':'dir'} len_dic1= Struct.pack ('I', Len (Json.dumps (DIC1))) Conn.send (Len_dic1+ Json.dumps (DIC1). Encode ('Utf-8') ) Conn.send (Json.dumps (os.listdir (file)). Encode ('Utf-8')) Down_load=os.path.abspath (file)Continue        elifos.path.isfile (file): Dic2= {'Tybe':'fil','down_size': Os.path.getsize (file)} Len_dic2= Struct.pack ('I', Len (Json.dumps (Dic2))) Conn.send (Len_dic2+ Json.dumps (dic2). Encode ('Utf-8')) with open (File,mode='RB') as F:down_size=os.path.getsize (file) whiledown_size:a= F.read (2048)                    Print(a)###########Conn.send (a) down_size-=Len (a) Break

#Client SideImportSocketImportstructImportOSImportJsonsk=socket.socket () Sk.connect ('127.0.0.1', 8989))defupload (): DiC= {'opt':'Upload','filename': None,'filesize': None} file= Input ('Please enter an absolute path to upload:') dic['filename'] =file dic['filesize'] =os.path.getsize (file) str_dic=json.dumps (DIC) Len_dic= Struct.pack ('I', Len (str_dic))#automatically converts the length of a dictionary to a length of 4 bytes typesSk.send (Len_dic + str_dic.encode ('Utf-8')) with open (dic['filename'],mode='RB') as F: whiledic['filesize'] >0:read_size= F.read (2048) sk.send (read_size) dic['filesize'] -=Len (read_size)defDownload (): DiC= {'opt':'Download','filename': None,'filesize': None} sk.send (Struct.pack ('I', Len (Json.dumps (DIC))) +json.dumps (DIC). Encode ('Utf-8'))     while1: LST= Json.loads (SK.RECV (2048). Decode ('Utf-8'))         forKvinchEnumerate (LST, 1):            Print(k, v) file= Input ('Please enter the file you want to download according to the serial number:') sk.send (lst[int (file)-1].encode ('Utf-8')) Len_dic= Struct.unpack ('I', SK.RECV (4)) [0] Str_dic= Sk.recv (Len_dic). Decode ('Utf-8')        ifJson.loads (Str_dic) ['Tybe'] =='dir':            Continue        elifJson.loads (Str_dic) ['Tybe'] =='fil': Down_file='D:\a\b\c\\'+lst[int (file)-1]             whileJson.loads (Str_dic) ['down_size']: With open (Down_file,mode='AB') as F:down_= SK.RECV (2048) F.write (down_) json.loads (str_dic) ['down_size'] -=Len (down_)if __name__=='__main__': LST= ['Upload','Download']    defmai (): forKvinchEnumerate (lst,1):            Print(k,v) C= Input ('Please enter the operation by ordinal:')        ifc = ='1': Upload ()ifc = ='2': Download ()Else:            Print('input Error!') mai ()

Python solves sticky packet phenomenon (struct module)