Golang TCP connection works, but UDP does not-CodePudding

I'm listening via netcat as such nc -lkp 1902

Whenever I make a tcp connection and try to send logs it works

        timeout := 30 * time.Second
    conn, err := net.DialTimeout("tcp", "localhost:1902", timeout)
    if err != nil {
        panic("Failed to connect to localhost:1902")
    }
    defer conn.Close()

    f := log.Ldate | log.Lshortfile
    logger := log.New(conn, "example-", f)
    logger.Println("This is a regular message1")
    logger.Println("This is a regular message2")
    logger.Println("This is a regular message3")
    logger.Println("This is a regular message4")
    logger.Println("This is a regular message5")
    logger.Println("This is a regular message6")

Output

example-2022/11/18 technique24.go:21: This is a regular message1
example-2022/11/18 technique24.go:22: This is a regular message2
example-2022/11/18 technique24.go:23: This is a regular message3
example-2022/11/18 technique24.go:24: This is a regular message4
example-2022/11/18 technique24.go:25: This is a regular message5
example-2022/11/18 technique24.go:26: This is a regular message6

But whenever I try to make a udp connection it does not work, could anyone explain why I get nothing on my logger?

        timeout := 30 * time.Second
    conn, err := net.DialTimeout("udp", "localhost:1902", timeout)
    if err != nil {
        panic("Failed to connect to localhost:1902")
    }
    defer conn.Close()

    f := log.Ldate | log.Lshortfile
    logger := log.New(conn, "example-", f)
    logger.Println("This is a regular message1")
    logger.Println("This is a regular message2")
    logger.Println("This is a regular message3")
    logger.Println("This is a regular message4")
    logger.Println("This is a regular message5")
    logger.Println("This is a regular message6")

Want to make a small poc for sending logs over udp to reduce backlog, tried to make a tcp connection first and it works fine but udp does not work, could anyone explain what I have to do to make it work?

CodePudding user response：

Netcat by default creates a TCP connection unless specified otherwise. For UDP connections, you need to use the -u flag of the netcat. From man page of netcat

-u Use UDP instead of the default option of TCP.

So changing your listener to nc -luk 1902 should fix the issue for UDP connections.