1 from socket import *
2 #Create socket
3 udp_server = socket(AF_INET,SOCK_DGRAM)
4
5 msg_server = ( "" ,8877 )
6 #Bind ip address and port
7 udp_server.bind(msg_server)
8
9 while True:
10 #Accept the message, note that recvfrom() is used here
11 msg_client = udp_server.recvfrom(1024 )
12
13 print ( "The new client is connected--->>> " )
14
15 if len(msg_client) !=0:
16 # There are two values in msg_client, the first one represents the content of the received message, and the second one represents the client's IP address and port information
17 print ( " %s:%s " % (msg_client[1] , msg_client[0].decode( " utf-8 " )))
18 else :
19 break
20
21 udp_server.close()
from socket import *
sock = socket (AF_INET, SOCK_DGRAM)
addr_msg = ( " 192.168.1.104 " ,8877 )
#Connect the server
sock.connect(addr_msg)
while True:
msg_send = input( " Please enter the message to be sent: " )
if msg_send == ' q ' :
break
#Note that sendto() is used here, where the first parameter indicates the content of the message to be sent, and the second parameter A tuple representing the IP address and port of the
server sock.sendto(msg_send.encode( " utf-8 " ),addr_msg)
sock.close()
1 from socket import *
2 import struct
3 import os
4
5 def main():
6 file_name = input( " Please enter the name of the file to download: " )
7 #Create a UDP socket
8 udpsocket = socket(AF_INET, SOCK_DGRAM)
9 #Create a tftp download request H indicates that the first parameter occupies two bytes, d indicates that the corresponding parameter is bite type
10 # %ds indicates the number of characters occupied by the file name, such as the following octet occupies 5 characters, so it is written as 5s
11 # octet is a mode of tftp transmission, which determines the format of the transmitted data, and there are several other modes of tftp transmission
12 #The package is constructed using pack in struck, where H means that the parameter occupies two bytes
13 request_header = struct.pack( " !H%dsb5sb " %len(file_name),1,file_name,0, " octet " , 0)
14
15 server_msg = ( " localhost " ,8888 )
16 #Send a request to download a file
17 udpsocket.sendto(request_header,server_msg)
18
19 f = open(file_name, " w " )
20
21 # num represents data The number of the block, here makes its initial value 0
22 num = 0
23 #Create a mark here to confirm that no errors occurred during transmission
24 mask = True
25
26 while True:
27 #Receive data packets from the server
28 response_data = udpsocket.recvfrom(1024 )
29 recv_data, server_info = response_data
30
31 #Here , use unpack in struct to unpack H, indicating that the data occupies two bytes in length
32 #The first two bytes here store the opcode
33 operation_num = struct.unpack( " !H " ,recv_data[: 2 ])
34 #The third and fourth bytes here store the number of the data block
35 package_num = struct.unpack( "!H " ,recv_data[2:4 ])
36
37 #When the opcode is 3, it means that the received information is a data packet sent by the server to the client after receiving the response
38 if operation_num [0] == 3 :
39 #This The value received at one time should be the result of adding one to the value received last time
40 num += 1
41 #This means that once the value of num exceeds the range of the value represented by its 2 bytes , then let it repeat from 0 (mainly because the opcode can only occupy 2 bytes) 42 if num == 65535 :
43 num = 0
44 #Confirm the block number 45 if num == package_num[0 ]: #The subscript is removed here because the package_num at this time represents a tuple, and the block number is the first data in the tuple 46 #Write the specific data received into the file
47 f.write(recv_data[4 :])
48 #The confirmation of the block number must add 1 to the previous value each time
49 num = package_num[0]
50 #Construct a response packet with an opcode of 4. The data sent is to add The block number after the last 1
51 ack_data = struct.pack( " !HH " ,4 ,package_num[0])
52 #Send response packet
53 udpsocket.sendto(ack_data, server_info)
54
55 elif operation_num[0] == 5 :
56 print ( " Error! " )
57 #If an error message occurs, change the value of the tag to False so that subsequent operations can delete the file
58 mask = False
59
60 #The maximum length of a data packet is 4+512 = 516 bits, if the data packet is less than this value, it means that this is the last data transmission
61 if len(recv_data) < 516 :
62 print ( " Cmplete! " )
63 break
64 # The value of the mask flag is True, which means that there is no error during the file transfer, and the locally received file is closed and saved
65 if mask == True:
66 f.close()
67
68 else :
69 # If the value of the mask flag is False, it means that there is an error message during the file transfer, then delete the received file
70 os.remove(file_name)
71
72 if __name__ == "__main":
73 main()