in reply to network debug

Sorry, I don't see what the solution is. The TCP dump stops just when it starts to get interesting.

Line 21 that you mention makes it look like several packets were lost and the sender kept sending "the next" packet hoping that the lost packets were just delayed and would eventually show up. After a while, the sender decides that it has been too long (more precisely, that the receiver's "window" for buffering out-of-order packets can't hold the next packet) and starts sending the lost packets. Right after sending the first lost packet and the reciever acknowledging it, the trace stops. But this is probably because you don't get any more packets for a while since this also looks like the place where the script hangs.

Other than the trace stopping, this is all stuff that I expect from TCP. I'm curious about the nature of the network connection between the two machines. If it is always stopping in the same place, then something is consistantly preventing those "lost" packets from getting through.

You may want to use TCP dump on both ends of the connection and see how they differ to narrow down where the packets are being lost. You'll probably find some packets that are not displayed in the trace above (and vice versa).

Also realize that TCP will usually wait 2 minutes for a lost packet so it can take 4 to 8 minutes before everything times out. You obviously haven't waited "forever" ;), but have you waited at least 8 minutes?

        - tye (but my friends call me "Tye")

Replies are listed 'Best First'.
Re: (tye)Re: network debug
by iic (Sexton) on Jun 14, 2001 at 22:15 UTC
    At first,Thanks for your reply!
    This time,I waitted for a long time.A change taked place.
    server.pl was run on Linux,client.pl was run on Win2k.
    They rapidly hung,

    status now: 
    E:\>perl client.pl 202.39.48.62 8000 socks5-v1.0r11.tar.gz
Begin ...
sent:21504

#perl server.pl 8000 tmpfile
Ready on port 8000 ...
client is coming ...
received:13300

    [download]

    about 10 minutes later,suddenly the sender loss his patience
    ,run up to the done directly.(the file's size is 404020)

    status now: 
    E:\>perl client.pl 202.39.48.62 8000 socks5-v1.0r11.tar.gz
Begin ...
sent:404020
Done.(local socks5-v1.0r11.tar.gz to remote 202.39.48.62)

#perl server.pl 8000 tmpfile
Ready on port 8000 ...
client is coming ...
received:13300

    [download]

    The receiver hold this pose at least 30 minutes,
    so I have to ctrl+c.

    tcpdump result: 
    <line 1:> a.2726 > b.8000: S 3628356093:3628356093(0) win 16384 <mss 1
+460,nop,nop,sackOK> (DF)
<line 2:> b.8000 > a.2726: S 2575239810:2575239810(0) ack 3628356094 w
+in 32120 <mss 1460,nop,nop,sackOK> (DF)
<line 3:> a.2726 > b.8000: . 1:1(0) ack 1 win 17520 (DF)
<line 4:> a.2726 > b.8000: P 1:513(512) ack 1 win 17520 (DF)
<line 5:> b.8000 > a.2726: . 1:1(0) ack 513 win 32120 (DF)
<line 6:> a.2726 > b.8000: P 513:1973(1460) ack 1 win 17520 (DF)
<line 7:> a.2726 > b.8000: P 1973:2049(76) ack 1 win 17520 (DF)
<line 8:> b.8000 > a.2726: . 1:1(0) ack 2049 win 32120 (DF)
<line 9:> a.2726 > b.8000: P 2049:3509(1460) ack 1 win 17520 (DF)
<line 10:> b.8000 > a.2726: . 1:1(0) ack 3509 win 32120 (DF)
<line 11:> a.2726 > b.8000: P 3509:4969(1460) ack 1 win 17520 (DF)
<line 12:> b.8000 > a.2726: . 1:1(0) ack 4969 win 32120 (DF)
<line 13:> a.2726 > b.8000: P 4969:6429(1460) ack 1 win 17520 (DF)
<line 14:> a.2726 > b.8000: P 6429:7889(1460) ack 1 win 17520 (DF)
<line 15:> b.8000 > a.2726: . 1:1(0) ack 7889 win 30660 (DF)
<line 16:> a.2726 > b.8000: P 7889:9349(1460) ack 1 win 17520 (DF)
<line 17:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 (DF)
<line 18:> a.2726 > b.8000: P 10753:11777(1024) ack 1 win 17520 (DF)
<line 19:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 <nop,nop, sack
+ 1 {10753:11777} > (DF)
<line 20:> a.2726 > b.8000: P 11777:13237(1460) ack 1 win 17520 (DF)
<line 21:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 <nop,nop, sack
+ 1 {10753:13237} > (DF)
<line 22:> a.2726 > b.8000: P 13237:13313(76) ack 1 win 17520 (DF)
<line 23:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 <nop,nop, sack
+ 1 {10753:13313} > (DF)
<line 24:> a.2726 > b.8000: P 14773:14849(76) ack 1 win 17520 (DF)
<line 25:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 <nop,nop, sack
+ 2 {14773:14849}{10753:13313} > (DF)
<line 26:> a.2726 > b.8000: P 14849:16309(1460) ack 1 win 17520 (DF)
<line 27:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 <nop,nop, sack
+ 2 {14773:16309}{10753:13313} > (DF)
<line 28:> a.2726 > b.8000: P 16309:16385(76) ack 1 win 17520 (DF)
<line 29:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 <nop,nop, sack
+ 2 {14773:16385}{10753:13313} > (DF)
<line 30:> a.2726 > b.8000: P 17845:17921(76) ack 1 win 17520 (DF)
<line 31:> b.8000 > a.2726: . 1:1(0) ack 9349 win 30660 <nop,nop, sack
+ 3 {17845:17921}{14773:16385}{10753:13313} > (DF)
<line 32:> a.2726 > b.8000: P 9349:9729(380) ack 1 win 17520 (DF)
<line 33:> b.8000 > a.2726: . 1:1(0) ack 9729 win 30280 <nop,nop, sack
+ 3 {17845:17921}{14773:16385}{10753:13313} > (DF)
<line 34:> a.2726 > b.8000: P 9729:11189(1460) ack 1 win 17520 (DF)
<line 35:> b.8000 > a.2726: . 1:1(0) ack 13313 win 29200 <nop,nop, sac
+k 2 {17845:17921}{14773:16385} > (DF)
<line 36:> a.2726 > b.8000: P 14773:16233(1460) ack 1 win 17520 (DF)
<line 37:> b.8000 > a.2726: . 1:1(0) ack 13313 win 30660 <nop,nop, sac
+k 2 {17845:17921}{14773:16385} > (DF)
<line 38:> b.8000 > a.2726: F 1:1(0) ack 13313 win 30660 <nop,nop, sac
+k 2 {17845:17921}{14773:16385} > (DF)
<line 39:> a.2726 > b.8000: R 3628369406:3628369406(0) win 0

    [download]


    My time is 2:20 am now.I can not go into the results
    carefully.May I send you email?see you next day:)
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