typeError: a byte-like object is required, not 'str' in Python 3

Question

I am new to python and I am experimenting things. I am trying to solve this UDP client and server program in python3 using python socket.

The objective of my UDP server program named UDpserver.py are as follows:

• Receives a message from a client
• Responds to the client with the same message but all in UPPER CASE.

The objective of a client program named UDpclient.py that connects to above server and receives a response from the server:

• sends a message to the server
• Display the message received from the server. The displayed message should be in upper case.

following is the server program's code (UDpserver.py):

from socket import *
serverPort = 12000
serverSocket = socket(AF_INET, SOCK_DGRAM)
serverSocket.bind(('', serverPort))
print (“The server is ready to receive”)
while 1:
 message, clientAddress = serverSocket.recvfrom(2048)
 modifiedMessage = message.upper()
 serverSocket.sendto(modifiedMessage, clientAddress)

Following is the client program code(UDpclient.py)

import socket
serverName = ‘hostname’
serverPort = 12000
clientSocket = socket.socket(socket.AF_INET,
 socket.SOCK_DGRAM)
message = input(’Input lowercase sentence:’)
clientSocket.sendto(message,(serverName, serverPort))
modifiedMessage, serverAddress = clientSocket.recvfrom(2048)
print modifiedMessage
clientSocket.close() 

When I run the client program(Udpclient.py) I get this error after it lets me input lowercase letters:

TypeError: a bytes-like object is required, not 'str' for line 7 ie clientSocket.sendto(message,(serverName, serverPort))

TypeError: a bytes-like object is required, not 'str'

If anybody could please help me solve this. Thank you.

Answer 1

You can use message.encode() to encode the string type message. So this is how your UDPclient.py would look like:

import socket
serverName = ‘hostname’
serverPort = 12000
clientSocket = socket.socket(socket.AF_INET,
 socket.SOCK_DGRAM)
message = input(’Input lowercase sentence:’)
clientSocket.sendto(message.encode(),(serverName, serverPort))
modifiedMessage, serverAddress = clientSocket.recvfrom(2048)
print modifiedMessage
clientSocket.close() 

Answer 2

Python 3 strings fully support the unicode specification. An in-memory string must be serialized in some way to conform to some sort of encoding such as ASCII, UTF-8, various Windows code pages and etc, before being sent on the network. sendto expects an already-encoded bytes string.

Since you are transfering data between machines, its not a good idea to let each one choose its own encoding. The easiest option for a home grown protocol is to just declare that you will use UTF-8, which is the most interoperable unicode encoding.

clientSocket.sendto(message.encode("utf-8"),(serverName, serverPort))

The receiver would decode using the same encoding.

Answer 3

将“主机名”更改为实际 IP 并使用以下命令更新错误代码后解决了该问题

clientSocket.sendto(message.encode(),(serverName, serverPort))