Thanks. I am going to write something outside the JDK to test it out. Maybe
I have a confused IP stack, who knows.
On Monday, February 29, 2016 at 2:21:36 AM UTC-6, drewhk wrote:
>
> Hi Val,
>
> I don't really know what is going on there, Akka works via JDK NIO and
> have no access to that low level TCP features. In other words, I really
> don't know what is going on on your machine and why you are seeing it, but
> I don't think we can do anything about it.
>
> -Endre
>
> On Mon, Feb 29, 2016 at 2:08 AM, Val P <injv...@gmail.com <javascript:>>
> wrote:
>
>> I am trying to understand why I'm seeing TCP retransmissions on a simple
>> program. I created a small program based on the 2.4.2 docs:
>>
>>
>> object HelloWorld {
>> def main(args: Array[String]): Unit = {
>> implicit val system = ActorSystem("Sys")
>> implicit val materializer = ActorMaterializer()
>>
>> val connections: Source[IncomingConnection, Future[Tcp.ServerBinding]] =
>> Tcp().bind("localhost", 8888)
>> connections runForeach { connection =>
>> // server logic, parses incoming commands
>> val commandParser = Flow[String].takeWhile(_ != "BYE").map(_ + "!")
>>
>> import connection._
>> val welcomeMsg = s"Welcome to: $localAddress, you are: $remoteAddress!"
>> val welcome = Source.single(welcomeMsg)
>>
>>
>> val serverLogic = Flow[ByteString]
>> .via(Framing.delimiter( ByteString("\n"), 256 ))
>> .map(_.utf8String)
>> .via(commandParser)
>> // merge in the initial banner after parser
>> .merge(welcome)
>> .map(_ + "\n")
>> .map(ByteString(_))
>>
>> connection.handleWith(serverLogic)
>> }
>> }
>> }
>>
>>
>>
>> But when I connect to localhost/8888 via telnet, type in a few lines, and
>> watch the traffic with wireshark, I'm seeing various retransmits and out of
>> order:
>>
>> 46482→8888 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1
>> TSval=47383693 TSecr=0 WS=128
>> 8888→46482 [SYN, ACK] Seq=0 Ack=1 Win=43690 Len=0 MSS=65495 SACK_PERM=1
>> TSval=47383693 TSecr=47383693 WS=128
>> 46482→8888 [ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=47383693 TSecr=47383693
>> 8888→46482 [PSH, ACK] Seq=1 Ack=1 Win=43776 Len=56 TSval=47383719
>> TSecr=47383693
>> 46482→8888 [ACK] Seq=1 Ack=57 Win=43776 Len=0 TSval=47383719
>> TSecr=47383719
>> [TCP Out-Of-Order] 46482→8888 [SYN] Seq=0 Win=43690 Len=0 MSS=65495
>> SACK_PERM=1 TSval=47383693 TSecr=0 WS=128
>> [TCP Retransmission] 8888→46482 [SYN, ACK] Seq=0 Ack=1 Win=43690 Len=0
>> MSS=65495 SACK_PERM=1 TSval=47383693 TSecr=47383693 WS=128
>> 46482→8888 [ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=47383693 TSecr=47383693
>> [TCP Retransmission] 8888→46482 [PSH, ACK] Seq=1 Ack=1 Win=43776 Len=56
>> TSval=47383719 TSecr=47383693
>> 46482→8888 [ACK] Seq=1 Ack=57 Win=43776 Len=0 TSval=47383719
>> TSecr=47383719
>> 46482→8888 [PSH, ACK] Seq=1 Ack=57 Win=43776 Len=6 TSval=47384746
>> TSecr=47383719
>> 8888→46482 [ACK] Seq=57 Ack=7 Win=43776 Len=0 TSval=47384746
>> TSecr=47384746
>> 8888→46482 [PSH, ACK] Seq=57 Ack=7 Win=43776 Len=7 TSval=47384747
>> TSecr=47384746
>> 46482→8888 [ACK] Seq=7 Ack=64 Win=43776 Len=0 TSval=47384747
>> TSecr=47384747
>> [TCP Retransmission] 46482→8888 [PSH, ACK] Seq=1 Ack=57 Win=43776 Len=6
>> TSval=47384746 TSecr=47383719
>> 8888→46482 [ACK] Seq=57 Ack=7 Win=43776 Len=0 TSval=47384746
>> TSecr=47384746
>> [TCP Retransmission] 8888→46482 [PSH, ACK] Seq=57 Ack=7 Win=43776 Len=7
>> TSval=47384747 TSecr=47384746
>> 46482→8888 [ACK] Seq=7 Ack=64 Win=43776 Len=0 TSval=47384747
>> TSecr=47384747
>> 46482→8888 [PSH, ACK] Seq=7 Ack=64 Win=43776 Len=6 TSval=47386128
>> TSecr=47384747
>> 8888→46482 [PSH, ACK] Seq=64 Ack=13 Win=43776 Len=7 TSval=47386129
>> TSecr=47386128
>> 46482→8888 [ACK] Seq=13 Ack=71 Win=43776 Len=0 TSval=47386129
>> TSecr=47386129
>> [TCP Retransmission] 46482→8888 [PSH, ACK] Seq=7 Ack=64 Win=43776 Len=6
>> TSval=47386128 TSecr=47384747
>> [TCP Retransmission] 8888→46482 [PSH, ACK] Seq=64 Ack=13 Win=43776 Len=7
>> TSval=47386129 TSecr=47386128
>> 46482→8888 [ACK] Seq=13 Ack=71 Win=43776 Len=0 TSval=47386129
>> TSecr=47386129
>>
>> Full trace at http://pastebin.com/09xi1kGa
>>
>> Could someone explain to me if I'm doing something wrong, or what's going
>> on?
>>
>>
>>
>>
>>
>>
>>
>> --
>> >>>>>>>>>> Read the docs: http://akka.io/docs/
>> >>>>>>>>>> Check the FAQ:
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>
--
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
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