Well blocking IO means that a given thread cannot do anything more until the IO is fully received (in the case of sockets this wait could be a long time). Non-blocking IO means an IO request is queued straight away and the function returns. The actual IO is then processed at some later point by … Read more
That’s just the way it’s defined. From the Open Group page for the open() function O_NONBLOCK When opening a FIFO with O_RDONLY or O_WRONLY set: If O_NONBLOCK is set: An open() for reading only will return without delay. An open() for writing only will return an error if no process currently has the file open … Read more
The standard approach is to use the select module. However, this doesn’t work on Windows. For that, you can use the msvcrt module’s keyboard polling. Often, this is done with multiple threads — one per device being “watched” plus the background processes that might need to be interrupted by the device.
In the case of a non blocking socket that has no data available, recv will throw the socket.error exception and the value of the exception will have the errno of either EAGAIN or EWOULDBLOCK. Example: import sys import socket import fcntl, os import errno from time import sleep s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((‘127.0.0.1’,9999)) fcntl.fcntl(s, fcntl.F_SETFL, … Read more
I see this is an old question, but I think something was missed here, that @nickdu attempted to point out but wasn’t quite clear. There are four types of IO pertinent to this discussion: Blocking IO Non-Blocking IO Asynchronous IO Asynchronous Non-Blocking IO The confusion arises I think because of ambiguous definitions. So let me … Read more
There is a server and a webframework. When should we use framework and when can we replace it with other one? This distinction is a bit blurry. If you are only serving static pages, you would use one of the fast servers like lighthttpd. Otherwise, most servers provide a varying complexity of framework to develop … Read more
As already stated, you can use sigaction to trap ctrl-c, or select to trap any standard input. Note however that with the latter method you also need to set the TTY so that it’s in character-at-a-time rather than line-at-a-time mode. The latter is the default – if you type in a line of text it … Read more
Asynchronous Asynchronous literally means not synchronous. Email is asynchronous. You send a mail, you don’t expect to get a response NOW. But it is not non-blocking. Essentially what it means is an architecture where “components” send messages to each other without expecting a response immediately. HTTP requests are synchronous. Send a request and get a … Read more
The biggest advantage of nonblocking or asynchronous I/O is that your thread can continue its work in parallel. Of course you can achieve this also using an additional thread. As you stated for best overall (system) performance I guess it would be better to use asynchronous I/O and not multiple threads (so reducing thread switching). … Read more
Synchronous vs Asynchronous Synchronous execution usually refers to code executing in sequence. Asynchronous execution refers to execution that doesn’t run in the sequence it appears in the code. In the following example, the synchronous operation causes the alerts to fire in sequence. In the async operation, while alert(2) appears to execute second, it doesn’t. Synchronous: … Read more