Python 中 TCP 连接的简单套接字编程练习； 错误：“无法建立连接，因为目标机器主动拒绝它”

Question

I am working on a very basic exercise designed to familiarize students with programming related to networks. This particular assignment is a common one as is described as follows:

In this assignment, you will learn the basics of socket programming for TCP connections in Python: how to create a socket, bind it to a specific address and port, as well as send and receive an HTTP packet. You will also learn some basics of HTTP header format. You can only use Python3.

You will develop a web server that handles one HTTP request at a time. Your web server should accept and parse the HTTP request, get the requested file from the server's file system, create an HTTP response message consisting of the requested file preceded by header lines, and then send the response directly to the client. If the requested file is not present in the server, the server should send an HTTP “404 Not Found” message back to the client.

Part one specification:

Put the attached HTML file (named HelloWorld.html) in the same directory in which the server webserver.py runs. Run the server program. Determine the IP address of the host that is running the server (eg, 128.238.251.26 or localhost). From another host, open a browser and provide the corresponding URL. For example: http://128.238.251.26:6789/HelloWorld.html . You can open a browser in the same host where the server runs and use the following http://localhost:6789/HelloWorld.html.

'HelloWorld.html' is the name of the file you placed in the server directory. Note also the use of the port number after the colon. You need to replace this port number with the port number that was assigned to you. In the above example, we have used port number 6789. The browser should then display the contents of HelloWorld.html. If you omit “:6789”, the browser will assume port 80 (why?), and you will get the web page from the server only if your server is listening at port 80.

Then try to get a file that is not present on the server (eg, test.html). You should get a “404 File Not Found” message.

Part Two specification:

Write your own HTTP client to test your server. Your client will connect to the server using a TCP connection, send an HTTP request to the server, and display the server response as an output. You can assume that the HTTP request sent is a GET method. The client should take command line arguments specifying the server IP address or hostname, the port at which the server is listening, and the HTTP file name (eg, test.html or HelloWorld.html). The following is an input command format to run the client. webclient.py <server_host> <server_port>

My code is for the Webserver is as follows:

#import socket module
from socket import *
import sys  # In order to terminate the program

serverSocket = socket(AF_INET, SOCK_STREAM)

# Prepare a sever socket
# Fill in start
serverHost = '192.168.1.4'
serverPort = 56014
serverSocket.bind((serverHost, serverPort))
serverSocket.listen(5)

# Fill in end
while True:
#establish connection
print('The server is ready to receive')

connectionSocket, addr = serverSocket.accept() # Fill in start             #Fill in end

try:

    message = connectionSocket.recv(4096) # Fill in start             #Fill in end

    filename = message.split()[1]

    f = open(filename[1:])

    outputdata = f.readlines() # Fill in start             #Fill in end

    # send one http header line in to the socket
    # Fill in start

    connectionSocket.send("HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n")
    connectionSocket.send("\r\n")

    # Fill in end

    # Send the content of the requested file to the connection socket
    for i in range(0, len(outputdata)):
        connectionSocket.send(outputdata[i].encode())
    connectionSocket.send("\r\n".encode())

    connectionSocket.close()

except IOError:
    # Send HTTP response code and message for file not found
    # Fill in start
    connectionSocket.send("HTTP/1.1 404 Not Found\r\n")
    connectionSocket.send("Content-Type: text/html\r\n")
    connectionSocket.send("\r\n")
    connectionSocket.send("<html><head></head><body><h1>404 Not Found</h1></body></html><\r\n>")

    # Fill in end
    # Close the client connection socket
    # Fill in start

    serverSocket.close()
    # Fill in end

serverSocket.close()
sys.exit()  # Terminate the program after sending the corresponding data

My code for the Webclient is as follows:

from socket import *
import sys
serverName = sys.argv[1]
serverPort = int(sys.argv[2])
fileName = sys.argv[3]
request = "GET "+str(fileName)+" HTTP/1.1"

clientSocket = socket(AF_INET, SOCK_STREAM)
clientSocket.connect((serverName, serverPort))
clientSocket.send(request.encode())
returnFromSever = clientSocket.recv(4096)

while(len(returnFromSever)>0):
    print(returnFromSever.decode())
    returnFromSever = clientSocket.recv(4096)
clientSocket.close()

The error I am receiving is:

"No connection could be made because the target machine actively refused it" 

Admittedly, I know almost nothing about network related programming and on top of that I am not familiar with the Python syntax (my entire degree program was exclusively in Java) so I am very lost here and somewhat desperate.

If anyone could please point me in the right direction as far as how to correct this error, I would be very deeply grateful.

Thanks

Answer 1

The error you are getting ( No connection could be made because the target machine actively refused it ) means that the port you are trying to connect to is not not being listened on the server. For example, if you try to connect to 192.168.1.1:80 (IP = 192.168.1.1 , port= 80 ) and the server on 192.168.1.1 doesn't listen on port 80 , you would receive this error.

A few things I would check in your case:

1. Is your server IP actually 192.168.1.4 ? If not, set it to the correct IP of the interface you want to listen on. If you want to listen on all the interfaces of the server, use this: serverHost = '0.0.0.0'
2. Does your client code attempt to connect to the server port? The server port is 56014 . You need to pass it as the second parameter of your client program (because of this line serverPort = int(sys.argv[2]) ).