making it short:
a server(192.168.0.78) listens on 8013
a client(10.0.2.15) tries to connect the server, getting its local port(eg.54591)
how to make the client close the connection and reuse 54591?
i tried and got:
1. close the connection directly and listen the same port:can not reuse port
2. launch another program(B) to connect server and exit, then tried to listen the port B has used:unknown port
is there a correct way to do this?
code is simple:
client
func main() {
conn, err := net.Dial("tcp" , "192.168.0.78:8013")
if err != nil {
panic(err)
}
localAddr := conn.LocalAddr().String()
conn.Close()
// i got the local port, what to do?
fmt.Println(localAddr)
}
server
func main(){
ln, err := net.Listen("tcp", ":8013")
if err != nil {
panic(err)
}
for i := 0; i < 5; i++ {
conn, err := ln.Accept()
if err != nil {
panic(err)
}
fmt.Println(conn.RemoteAddr().String(), "connected")
conn.Close()
}
}
If you want a client to use a specific local port number, you must bind() after you create() but before you connect(). You can specify any local port number (and/or specific interface) with bind.
To reuse a previous port number, you have to make that port number known to the next connection attempt and you must open it with the SO_REUSEADDR "reuse" option each time or the second bind will not be allowed until the first one fully expires (often 2 minutes after it was closed).
Those are C function names. Go will have something similar.
This is a known problem of Go's net package.
There are couple of workarounds, like this package, for instance: https://github.com/jbenet/go-reuseport