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POWireshark TCP Dup ACK - strange
 

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  1. POWireshark TCP Dup ACK - strange
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    <p>I have run Wireshark on the server's computer and I have such a strange transmission:</p> <p>Client (X: src port 65509) connects to my server (Y: dst port 9999). </p> <p>1) There is normal TCP handshake</p> <pre><code>15:47:41.921228 XXX.XXX.XXX.XXX 65509 YYY.YYY.YYY.YYY 9999 65509 &gt; distinct [SYN] Seq=0 Win=8688 Len=0 MSS=1460 WS=0 SACK_PERM=1 TSV=66344090 TSER=0 15:47:41.921308 YYY.YYY.YYY.YYY 9999 XXX.XXX.XXX.XXX 65509 distinct &gt; 65509 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 SACK_PERM=1 TSV=69754693 TSER=66344090 15:47:42.176823 XXX.XXX.XXX.XXX 65509 YYY.YYY.YYY.YYY 9999 65509 &gt; distinct [ACK] Seq=1 Ack=1 Win=8688 Len=0 TSV=66344350 TSER=69754693 </code></pre> <p>2) Server sends an encryption key to the client and client ACKs receiving it:</p> <pre><code>15:47:42.180755 YYY.YYY.YYY.YYY 9999 XXX.XXX.XXX.XXX 65509 distinct &gt; 65509 [PSH, ACK] Seq=1 Ack=1 Win=65160 Len=24 TSV=69754719 TSER=66344350 15:47:42.452606 XXX.XXX.XXX.XXX 65509 YYY.YYY.YYY.YYY 9999 65509 &gt; distinct [ACK] Seq=1 Ack=25 Win=8664 Len=0 TSV=66344630 TSER=69754719 </code></pre> <p>3) Suddenly panel Resets the connection for some reason</p> <pre><code>15:47:42.948618 XXX.XXX.XXX.XXX 65509 YYY.YYY.YYY.YYY 9999 65509 &gt; distinct [RST] Seq=28 Win=0 Len=0 </code></pre> <p><strong>4) But the strange thing to me goes here. Server sends TCP Dup ACK. What can be the reason for that? I thought this message can be sent only after retransmission or sth. I've never seen it to be sent after RST.</strong></p> <pre><code>15:47:42.948654 YYY.YYY.YYY.YYY 9999 XXX.XXX.XXX.XXX 65509 [TCP Dup ACK 5856#1] distinct &gt; 65509 [ACK] Seq=25 Ack=1 Win=65160 Len=0 TSV=69754796 TSER=66344630** </code></pre> <p>5) Client sends RST again.</p> <pre><code>15:47:43.227269 XXX.XXX.XXX.XXX 65509 YYY.YYY.YYY.YYY 9999 65509 &gt; distinct [RST] Seq=1 Win=0 Len=0 </code></pre> <p>Thanks for any suggestions.</p>
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    1. COStackoverflow is intended for questions related to programming (see the faq, http://stackoverflow.com/faq). Your question does not give any indication that programming is involved.
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      1. USSjoerd C. de Vries
    2. COSjoerd, have you read the faq your are linking to? [cut] ...but if your question generally covers … * software tools commonly used by programmers * matters that are unique to the programming profession … then you’re in the right place to ask your question! [/cut] Isn't Wireshark one of such a tools or matters unique to the programming profession?
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    3. COAs far as I can judge your problems are not about Wireshark as a programmer's tool but about the results you obtained using Wireshark as a diagnostic instrument. From the phrasing of your question it looks like your problems lies somewhere in the communication between client and server. Either the SuperUser or the ServerFault sites seem to be more appropriate sites for such questions.
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      1. USSjoerd C. de Vries
 

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