CODEWITHSUNDEEP
go
Elaheh
Elaheh

Reputation: 87

How to drop a UDP connection between server and client from server side in Golang?

I'm trying to find a standard way to close a connection between a client and server in a UDP connection.

Currently, I came up with the following solution, however, I'm not sure whether this is an idiomatic way or not?

Basically what I'm doing here on the server-side (handleClient function) is to conn.WriteTo(nil, Addr) which write nil to the UDP address. on the client side I check if the read() function retrieved any data or not, in case the number of the reading byte is zero, the client gives up on reading.

if n ==0 || err != nil {
        break
    }

Here is my simplified Server.go file:

func handleClient(conn *net.UDPConn) {
    b := make([]byte, 1024)

    n, Addr, err := conn.ReadFrom(b[0:])
    if err != nil {
        panic(err)
    }

    fmt.Println("read: ", n, " bytes", Addr.String())
    // write the data back to the client, just for debug purpose
    conn.WriteTo(b[0:n], Addr)
    // let the client know that server has no more data 
    conn.WriteTo(nil, Addr)
}

And this is my client.go file

    conn, err := net.Dial("udp", ":14000")
if err != nil {
    panic(err)
}
defer conn.Close()

conn.Write([]byte("I'm client "))

for {
    b := make([]byte, 512)
    n, err := conn.Read(b)
    if n ==0 || err != nil {
        fmt.Println(">", n, err)
        break
    }
    fmt.Println(string(b))
}
fmt.Println("finished.")

Upvotes: 0

Views: 707

Answers (1)

Dylan Reimerink
Dylan Reimerink

Reputation: 7978

There is no standard way to do this. UDP is a stateless protocol so there is no "connection" like you would have with a TCP connection. DNS for example has no concept of a state, a client sends a request and the server will respond, no state is maintained, this is usually the selling point of UDP.

The applications are responsible for maintain state, so if you want a stateful protocol on top of UDP you also have to handle closing such a connection yourself. You might take inspiration from FTP or TFTP on how to implement this. Or consider using a stateful transport layer protocol like TCP or QUIC to handle stateful connections for you.

Upvotes: 1

Related Questions