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This article mainly explains how to solve the problem of port occupation after python process ends. Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let Xiaobian take you to learn "how to solve the problem of port occupation after python process ends"!

socket allocation

A server-side process requests a scoket from the operating system to listen, but when the process exits, the connection that has not been closed does not disappear immediately, but is left to the operating system to handle. The operating system will try to close the connection. However, if there is a problem when closing, the connection will always be in TIME_WAIT or other abnormal state, and this is the corresponding port is still in the occupied state. If the server program is restarted at this time, the address will be occupied.

example

Test Code:

import sockets = socket.socket()s.bind(('0.0.0.0', 12345))s.listen()(client, addr) = s.accept()print(client)print(addr)

Connect with NC:

nc 127.0.0.1 12345

The server prints client and addr and exits normally, but in this case netstat -anop is used| grep 12345 Check and find that the corresponding connection is not immediately released

tcp 0 0 127.0.0.1:12345 127.0.0.1:59408 TIME_WAIT - timewait (28.18/0/0)

At this time, start the server again and find that the error is reported:

Traceback (most recent call last): File "server.py", line 5, in s.bind(('0.0.0.0', 12345))OSError: [Errno 98] Address already in use Solution

Using setsockopt:

import sockets = socket.socket()s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)s.bind(('0.0.0.0', 12345))s.listen()(client, addr) = s.accept()print(client)print(addr)

At this point, the address will not appear occupied prompt

There are the same methods in c, but the method declarations are different. The usage of version c is

struct sockaddr_in addr;addr.sin_family = AF_INET;addr.sin_port = htons(12345);addr.sin_addr.s_addr = htonl(INADDR_ANY);int s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);int reuse = 1;setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));bind(s, (struct sockaddr *) &addr, sizeof(addr))listen(s, )struct sockaddr_in in_addr;int len = sizeof(in_addr);int client = accept(socket, (struct sockaddr *) in_addr, &len);//handle client//... other

Found that in addition to SO_REUSEADDR there is also an option SO_REUSEPORT, query found that it is unique to BSD, Linux and can not be used

If the client binds the port with this attribute, the server may receive a FIN for no reason as soon as it connects, causing it to close immediately. Therefore, the client should pay attention when using this option.

At this point, I believe that everyone has a deeper understanding of "how to solve the problem of port occupation after the python process is over." Let's actually operate it! Here is the website, more related content can enter the relevant channels for inquiry, pay attention to us, continue to learn!

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