# udp.ludic — Udp.* on the loopback: two sockets, one datagram each way.
program UdpDemo {
  entry {
    let a = Udp.open(0)
    let b = Udp.open(0)
    let pa = Udp.port(a)
    let pb = Udp.port(b)
    let lo = Udp.ip("127.0.0.1")
    let out = buffer(16)
    out[0] = 104
    out[1] = 105
    let sent = Udp.send(a, lo, pb, out, 2)
    let inb = buffer(64)
    var got = 0
    var tries = 0
    while got == 0 and tries < 200000 { got = Udp.recv(b, inb, 64);  tries += 1 }
    let from_ok = Udp.from_ip(b) == lo and Udp.from_port(b) == pa
    Udp.send(b, Udp.from_ip(b), Udp.from_port(b), inb, got)
    var back = 0
    tries = 0
    while back == 0 and tries < 200000 { back = Udp.recv(a, out, 16);  tries += 1 }
    let bad = Udp.ip("1.2.3") == 0 and Udp.ip("300.1.1.1") == 0
    print(`{sent} {got} {inb[0]} {inb[1]} {from_ok} {back} {Udp.ip_text(lo)} {bad} {Udp.recv(a, out, 16)} {pa > 0}`)
    Udp.close(a)
    Udp.close(b)
  }
}