拨号错误：“打开的文件太多”

I am trying to write TCP client-server program, to find the maximum number of concurrent connection handled by server. So I create a simple server and initiated multiple tcp connection (using go routine).

server.go

func main() {
    ln, err := net.Listen("tcp", ":9100")
    if err != nil {
        fmt.Println(err.Error())
    }
    defer ln.Close()
    fmt.Println("server has started")

    for {
        conn, err := ln.Accept()
        if err != nil {
            fmt.Println(err.Error())
        }
        conn.Close()
        fmt.Println("received one connection")
    }

}

client.go

func connect(address string, wg *sync.WaitGroup) {
    conn, err := net.Dial("tcp", address)
    if err != nil {
        fmt.Println(err.Error())
        os.Exit(-1)
    }
    defer conn.Close()

    fmt.Println("connection is established")
    wg.Done()
}

func main() {
    var wg sync.WaitGroup
    for i := 0; i < 10000; i++ {
        wg.Add(1)
        fmt.Printf("connection %d", i)
        fmt.Println()
        go connect(":9100", &wg)
    }

    wg.Wait()
    fmt.Print("all the connection served")
}

I was expecting that server will become unresponsive because of TCP SYN attach but my client application got crashed after ~2000 connection request. Following is the error message :

dial tcp :9100: too many open files
exit status 255

I need help for the following questions :

• What are the required changes in client.go to emulate the TCP connection flooding on my go server.

• How could I increase the number of open FD (mac OS), if there is limitation of maximum open FD for a precess.

• What is the default TCP queue size for the Listen() (in C programming language, queue size is specified in the listen(fd, queue_size)).

Edit :

• I found some help (question #2) for increasing the number of open file descriptor, but it is not working (no change in client error message).

ulimit settings

$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
file size               (blocks, -f) unlimited
max locked memory       (kbytes, -l) unlimited
max memory size         (kbytes, -m) unlimited
open files                      (-n) 10000
pipe size            (512 bytes, -p) 1
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 709
virtual memory          (kbytes, -v) unlimited