Wireshark-users: Re: [Wireshark-users] wireshark shows: TCP Port numbers reused on PlanetLab node
Date Index · Thread Index · Other Months · All Mailing Lists
Date Prev · Date Next · Thread Prev · Thread Next
From: Martin Visser <martinvisser99@xxxxxxxxx>
Date: Fri, 22 Mar 2013 06:46:56 +1100
Very simply, you have have captured the packets 1 and 2 out of order. Packet 2 it would seem is the SYN,  that initiated the SYN-ACK in packet 1. (At least it seems that way to me - a sane stack wouldn't reuse the same TCP source port at such a small interval). Are you running a teamed physical interface, and hence why you are capturing packets out of order?.



On 21 March 2013 00:18, wen lui <esolvepolito@xxxxxxxxx> wrote:
I run a simple TCP client on machine A and a simple TCP server on machine B (machine B is a Planetlab node while machine A is not).
Then the client establishes a tcp connection with machine B and send some data.
I capture packets on both A and B, on A the wireshark shows that it is a normal 3-Way handshaking, but on B, it shows as below:

1	0.000000	138.46.116.22	138.46.201.109	TCP	74	54000 > 57182 [SYN, ACK] Seq=0 Ack=0 Win=5792 Len=0 MSS=1460 SACK_PERM=1 TSval=1751648211 TSecr=1119925943 WS=128 0.000000


2	-0.000062	138.46.201.109	138.46.116.22	TCP	74	[TCP Port numbers reused] 57182 > 54000 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=1119925943 TSecr=0 WS=128	-0.000062
3	0.000308	138.46.201.109	138.46.116.22	TCP	66	57181 > 54000 [ACK] Seq=1 Ack=1 Win=14720 Len=0 TSval=1119737278 TSecr=1751459556	0.000308



while I see on machine B, actually the tcp connection is established.
before the client sends the SYN and ACK, I checked machine B and found no TCP connection

netstat -tnp
(Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.)
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address               Foreign Address                State       PID/Program name   
tcp        0      0 138.46.116.22:54000         138.46.201.109:57181        ESTABLISHED 17879/tcp_server 


anyway, I can send data to the tcp server and it receives it correctly.



why wireshark shows TCP Port numbers reused? and the time is '-0.000062'?


___________________________________________________________________________
Sent via:    Wireshark-users mailing list <wireshark-users@xxxxxxxxxxxxx>
Archives:    http://www.wireshark.org/lists/wireshark-users
Unsubscribe: https://wireshark.org/mailman/options/wireshark-users
             mailto:wireshark-users-request@xxxxxxxxxxxxx?subject=unsubscribe