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:)