循环运行时间（真的很慢）

Question

Following is my code:

import socket
import time
mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect(('www.py4inf.com', 80))
mysock.send(b'GET /code/romeo.txt HTTP/1.1\n')
mysock.send(b'Host: www.py4inf.com\n\n')
all = b""

while True:
    data = mysock.recv(512)
    all = all + data
    if len(data) < 1:
        break

mysock.close()

stuff = all.decode()
position = stuff.find('\r\n\r\n')
print(stuff[position+4:])

There must be something wrong because it takes almost 30 seconds to invoke break in while loop. However, if I change the code if len(data) < 1: to if len(data) < 100: it took just 0.5 second.

Please help. It haunted me for a while. The sample website: http://www.py4inf.com/code/romeo.txt

Answer 1

Web servers don't have to close connections immediately.In fact, they may be looking for another http request. Just add print(data) after the recv and you'll see you get the data, then a pause, then b'' , meaning the server finally closed the socket.

You'll also notice that the server sends a header that includes "Content-Length: 167\\r\\n". Once the header has finished, the server will send exactly 167 bytes of data. You could parse out the header yourself but that's why we have client libraries like urllib and requests .

I was curious about how much would need to be added to the request header to get the connection to close immediately, and Connection: close seemed to do it. This returns right away:

import socket
import time
mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect(('www.py4inf.com', 80))
mysock.send(b'GET /code/romeo.txt HTTP/1.1\n')
mysock.send(b'Connection: close\n')
mysock.send(b'Host: www.py4inf.com\n\n')
all = b""

while True:
    data = mysock.recv(512)
    all = all + data
    if len(data) < 1:
        break

mysock.close()

stuff = all.decode()
position = stuff.find('\r\n\r\n')
print(stuff[position+4:])