How to properly send HTTP response with Python usi

2020-05-16 05:41发布

站内问答 / Python
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I have a very simple web sever written in Python. It listens on port 13000, how can I make it deliver a simple "Hello World" webpage if http://localhost:13000 is opened in browser?

Right there is my code:

# set up socket and connection
while True:
    sock, addr = servSock.accept()
    # WHAT GOES HERE?
    sock.close()

As you can see, I am not exactly sure how to actually send back the webpage?

I only have to use the socket library.

EDIT: The problem is not that I don't know how to formulate the HTTP response, I don't know how to actually make it display in my browser! It just keeps spinning/loading.

6条回答
姐就是有狂的资本
2楼-- · 2020-05-16 06:03

Updated according to question change

Possibly, it keeps spinning because in combination of absense of Content-Length and Connection headers, browser may assume it's Connection: keep-alive, so it continues to receive data from your server forever. Try to send Connection: close, and pass actual Content-Length to see if that helps.

Won't this do what you expect it to? :)

#!/usr/bin/env python
# coding: utf8

import socket

MAX_PACKET = 32768

def recv_all(sock):
    r'''Receive everything from `sock`, until timeout occurs, meaning sender
    is exhausted, return result as string.'''

    # dirty hack to simplify this stuff - you should really use zero timeout,
    # deal with async socket and implement finite automata to handle incoming data

    prev_timeout = sock.gettimeout()
    try:
        sock.settimeout(0.01)

        rdata = []
        while True:
            try:
                rdata.append(sock.recv(MAX_PACKET))
            except socket.timeout:
                return ''.join(rdata)

        # unreachable
    finally:
        sock.settimeout(prev_timeout)

def normalize_line_endings(s):
    r'''Convert string containing various line endings like \n, \r or \r\n,
    to uniform \n.'''

    return ''.join((line + '\n') for line in s.splitlines())

def run():
    r'''Main loop'''

    # Create TCP socket listening on 10000 port for all connections, 
    # with connection queue of length 1
    server_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, \
                                socket.IPPROTO_TCP)
    server_sock.bind(('0.0.0.0', 13000))
    server_sock.listen(1)

    while True:
        # accept connection
        client_sock, client_addr = server_sock.accept()

        # headers and body are divided with \n\n (or \r\n\r\n - that's why we
        # normalize endings). In real application usage, you should handle 
        # all variations of line endings not to screw request body
        request = normalize_line_endings(recv_all(client_sock)) # hack again
        request_head, request_body = request.split('\n\n', 1)

        # first line is request headline, and others are headers
        request_head = request_head.splitlines()
        request_headline = request_head[0]
        # headers have their name up to first ': '. In real world uses, they
        # could duplicate, and dict drops duplicates by default, so
        # be aware of this.
        request_headers = dict(x.split(': ', 1) for x in request_head[1:])

        # headline has form of "POST /can/i/haz/requests HTTP/1.0"
        request_method, request_uri, request_proto = request_headline.split(' ', 3)

        response_body = [
            '<html><body><h1>Hello, world!</h1>',
            '<p>This page is in location %(request_uri)r, was requested ' % locals(),
            'using %(request_method)r, and with %(request_proto)r.</p>' % locals(),
            '<p>Request body is %(request_body)r</p>' % locals(),
            '<p>Actual set of headers received:</p>',
            '<ul>',
        ]

        for request_header_name, request_header_value in request_headers.iteritems():
            response_body.append('<li><b>%r</b> == %r</li>' % (request_header_name, \
                                                    request_header_value))

        response_body.append('</ul></body></html>')

        response_body_raw = ''.join(response_body)

        # Clearly state that connection will be closed after this response,
        # and specify length of response body
        response_headers = {
            'Content-Type': 'text/html; encoding=utf8',
            'Content-Length': len(response_body_raw),
            'Connection': 'close',
        }

        response_headers_raw = ''.join('%s: %s\n' % (k, v) for k, v in \
                                                response_headers.iteritems())

        # Reply as HTTP/1.1 server, saying "HTTP OK" (code 200).
        response_proto = 'HTTP/1.1'
        response_status = '200'
        response_status_text = 'OK' # this can be random

        # sending all this stuff
        client_sock.send('%s %s %s' % (response_proto, response_status, \
                                                        response_status_text))
        client_sock.send(response_headers_raw)
        client_sock.send('\n') # to separate headers from body
        client_sock.send(response_body_raw)

        # and closing connection, as we stated before
        client_sock.close()

run()

For more detailed description, please see description of HTTP protocol.

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forever°为你锁心
3楼-- · 2020-05-16 06:05 
# set up socket and connection
while True:
sock, addr = servSock.accept()
sock.send("HTTP/1.1 200 OK\n"
         +"Content-Type: text/html\n"
         +"\n" # Important!
         +"<html><body>Hello World</body></html>\n");
sock.close()
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仙女界的扛把子
4楼-- · 2020-05-16 06:10

or, if you just don't want to remember the full protocol, you can find it again using :

 % nc stackoverflow.com 80
GET / HTTP/1.1
Host: stackoverflow.com

HTTP/1.1 200 OK
Cache-Control: public, max-age=60
Content-Type: text/html; charset=utf-8
Expires: Wed, 11 Apr 2012 21:33:49 GMT
Last-Modified: Wed, 11 Apr 2012 21:32:49 GMT
Vary: *
Date: Wed, 11 Apr 2012 21:32:49 GMT
Content-Length: 206008

[...]
 %

well, you shall usually prefer a site that is less verbose (usually serving only a static file) than stackoverflow ;)

The minimal requirements (you'll find on the answer) is :

sock.send(r'''HTTP/1.0 200 OK
Content-Type: text/plain

Hello, world!

''')

two returns are mandatory for the server to get the answer, otherwise the browser waits indefinitely for headers

But to mimic the behaviour of a webserver, don't forget to send your answer only after the browser sends you some data followed by two carriage returns, usually you can get what it sends using : 

 % nc -kl localhost 13000
GET / HTTP/1.1
Host: localhost:13000
User-Agent: Mozilla/5.0...
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
DNT: 1
Connection: keep-alive

 %

so you can improve your test routines

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甜甜的少女心
5楼-- · 2020-05-16 06:13

I took a previous answer and edited the code for Python3 utf-8 and bytes encoding. Thanks for the original answer it helped out a lot.

import socket

MAX_PACKET = 32768

def recv_all(sock):
    r'''Receive everything from `sock`, until timeout occurs, meaning sender
    is exhausted, return result as string.'''

    # dirty hack to simplify this stuff - you should really use zero timeout,
    # deal with async socket and implement finite automata to handle incoming data

    prev_timeout = sock.gettimeout()
    try:
        sock.settimeout(0.1)

        rdata = []
        while True:
            try:
                # Gotta watch for the bytes and utf-8 encoding in Py3
                rdata.append(sock.recv(MAX_PACKET).decode('utf-8')) 
            except socket.timeout:
                return ''.join(rdata)

        # unreachable
    finally:
        sock.settimeout(prev_timeout)

def normalize_line_endings(s):
    r'''Convert string containing various line endings like \n, \r or \r\n,
    to uniform \n.'''
    test = s.splitlines()
    return ''.join((line + '\n') for line in s.splitlines())

def run():
    r'''Main loop'''

    # Create TCP socket listening on 10000 port for all connections,
    # with connection queue of length 1
    server_sock = socket.socket(socket.AF_INET,
                                socket.SOCK_STREAM,
                                socket.IPPROTO_TCP)
    #Added the port 13001 for debuging purposes 

    try:
        server_sock.bind(('0.0.0.0', 13000))
        print('PORT 13000')
    except:
        server_sock.bind(('0.0.0.0', 13001))
        print('PORT 13001')
    # except:
    #     server_sock.bind(('0.0.0.0', 13002))
    #     print('PORT 13002')

    server_sock.listen(1)

    while True:
        # accept connection
        try:
            client_sock, client_addr = server_sock.accept()

            # headers and body are divided with \n\n (or \r\n\r\n - that's why we
            # normalize endings). In real application usage, you should handle
            # all variations of line endings not to screw request body
            request = normalize_line_endings(recv_all(client_sock)) # hack again

            request_head, request_body = request.split('\n\n', 1)

            # first line is request headline, and others are headers
            request_head = request_head.splitlines()
            request_headline = request_head[0]
            # headers have their name up to first ': '. In real world uses, they
            # could duplicate, and dict drops duplicates by default, so
            # be aware of this.
            request_headers = dict(x.split(': ', 1) for x in request_head[1:])

            # headline has form of "POST /can/i/haz/requests HTTP/1.0"
            request_method, request_uri, request_proto = request_headline.split(' ', 3)

            response_body = [
                '<html><body><h1 style="color:red">Hello, world!</h1>',
                '<p>This page is in location %(request_uri)r, was requested ' % locals(),
                'using %(request_method)r, and with %(request_proto)r.</p>' % locals(),
                '<p>Request body is %(request_body)r</p>' % locals(),
                '<p>Actual set of headers received:</p>',
                '<ul>',
            ]

            for request_header_name, request_header_value in request_headers.items():
                response_body.append('<li><b>%r</b> == %r</li>' % (request_header_name,
                                                                    request_header_value))

            response_body.append('</ul></body></html>')

            response_body_raw = ''.join(response_body)

            # Clearly state that connection will be closed after this response,
            # and specify length of response body
            response_headers = {
                'Content-Type': 'text/html; encoding=utf8',
                'Content-Length': len(response_body_raw),
                'Connection': 'close',
            }

            response_headers_raw = ''.join('%s: %s\n' % (k, v) for k, v in \
                                                    response_headers.items())

            # Reply as HTTP/1.1 server, saying "HTTP OK" (code 200).
            response_proto = 'HTTP/1.1'.encode()
            response_status = '200'.encode()
            response_status_text = 'OK'.encode() # this can be random

            # sending all this stuff
            client_sock.send(b'%s %s %s' % (response_proto, response_status,
                                                            response_status_text))
            client_sock.send(response_headers_raw.encode())
            client_sock.send(b'\n') # to separate headers from body
            client_sock.send(response_body_raw.encode())

            # and closing connection, as we stated before

        finally:
            client_sock.close()

run()
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Viruses.
6楼-- · 2020-05-16 06:16

You might want to Checkout web objects http://www.webob.org/

It's a simple lightweight project for creating http compatible requests and responses. You can do just about anything with you requests/response objects ... Or just delegate the heavy lifting to WebObjects

Sample

>>> from webob import Response
>>> res = Response()
>>> res.status
'200 OK'
>>> res.headerlist
[('Content-Type', 'text/html; charset=UTF-8'), ('Content-Length', '0')]
>>> res.body
''
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Explosion°爆炸
7楼-- · 2020-05-16 06:23

Send back something like:

HTTP/1.1 200 OK
Date: Wed, 11 Apr 2012 21:29:04 GMT
Server: Python/6.6.6 (custom)
Content-Type: text/html

Then the actual html code. Make sure there is a newline after the Content-Type line and before the html.

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