CODEWITHSUNDEEP
socketstcpnetwork-programmingoperating-systemserversocket
qifan
qifan

Reputation: 7

how does Operating System map port number to process that use it

For a simple python server using TCP socket as below, when there comes a TCP packet, and transport layer get port number, how does OS/transport layer know which thread/process to wake up(assuming the thread/process is blocking because of recv() system call)? for the code below, both parent thread and child thread have the connectionsocket file descriptor, how OS know which one to wake up? Thanks

host = 'localhost'
port = 55567
buf = 1024
addr = (host, port)
welcomesocket = socket(AF_INET, SOCK_STREAM)
welcomesocket.bind(addr)
welcomesocket.listen(2)

while 1:
    connectionsocket, clientaddr = serversocket.accept()
    thread.start_new_thread(handler, (connectionsocket, clientaddr))
serversocket.close()

Upvotes: 0

Views: 944

Answers (1)

Zang MingJie
Zang MingJie

Reputation: 5275

There is an hash map tracking all used port in the kernel space.

When a packet arrives, kernel lookup the table using the port information in the packet, find the associated socket, and notify it

Here is how linux do it http://lxr.free-electrons.com/source/net/ipv4/udp.c#L489

Upvotes: 0

Related Questions