Date: Fri, 16 Feb 96 10:04:06 MET From: Greg Lehey <lehey.pad@sni.de> To: hackers@freebsd.org (Hackers; FreeBSD) Subject: Tracing HTTP connections Message-ID: <199602160908.KAA25178@nixpbe.pdb.sni.de>
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OK, this is off topic for FreeBSD, but I suspect that somebody here will have some useful input. I have a strange problem with a web server here, and I'm trying to figure out what's going on. The problem is that neither requestor nor server give me a useful error message. The server is the CERN server, and we've tried with a number of requestors, ranging from Mosaic and Netscape on UNIX to Internet Explorer (?) on Windoze 95%. In each case, on bit map images only, the requestor sporadically reports an "unable to connect messsage" after about 20 seconds. We've run tcpdump on the connection, but I can't recognize anything without knowing the protocol. Where can I find it? FWIW, here's a section where I suspect that something has gone wrong: 10:20:40.56 pcd72097.1055 > SMABSZ16.http: S 8161300:8161300(0) win 8192 <mss 1460> (DF) 4500 002C 9207 4000 * 2006 A862 5911 643F E~~,~~@~ ~(bY~d? 5911 0A01 041F 0050 * 007C 8814 0000 0000 Y~~~~~~P~|~~~~~~ 6002 2000 CAC4 0000 * 0204 05B4 B4B4 `~ ~JD~~~~~444 10:20:40.56 SMABSZ16.http > pcd72097.1055: S 5640705:5640705(0) ack 8161301 win 32767 <mss 1460> 4500 002C BCA6 0000 * 4006 9DC3 5911 0A01 E~~,<&~~@~~CY~~~ 5911 643F 0050 041F * 0056 1201 007C 8815 Y~d?~P~~~V~~~|~~ 6012 7FFF 585D 0000 * 0204 05B4 0000 `~~X]~~~~~4~~ 10:20:40.56 pcd72097.1055 > SMABSZ16.http: . ack 1 win 8760 (DF) 4500 0028 9307 4000 * 2006 A766 5911 643F E~~(~~@~ ~'fY~d? 5911 0A01 041F 0050 * 007C 8815 0056 1202 Y~~~~~~P~|~~~V~~ 5010 2238 CDE1 0000 * 0000 0000 0000 P~"8Ma~~~~~~~~ 10:20:40.60 pcd72097.1055 > SMABSZ16.http: P 1:233(232) ack 1 win 8760 (DF) 4500 0110 9407 4000 * 2006 A57E 5911 643F E~~~~~@~ ~%~Y~d? 5911 0A01 041F 0050 * 007C 8815 0056 1202 Y~~~~~~P~|~~~V~~ 5018 2238 DCF0 0000 * 4745 5420 2F63 6769 P~"8\p~~GET /cgi 2D62 696E 2F68 7469 * 6D61 6765 2F6D 6170 -bin/htimage/map 732F 7765 6C63 6F6D * 652E 6D61 703F 3238 s/welcome.map?28 312C 3336 2048 5454 * 502F 312E 300D 0A52 1,36 HTTP/1.0~~R 6566 6572 6572 3A20 * 6874 7470 3A2F 2F38 eferer: http://8 392E 3137 2E31 302E * 312F 0D0A 436F 6E6E 9.17.10.1/~~Conn 6563 7469 6F6E 3A20 * 4B65 6570 2D41 6C69 ection: Keep-Ali 7665 0D0A 5573 6572 * 2D41 6765 6E74 3A20 ve~~User-Agent: 4D6F 7A69 6C6C 612F * 322E 3062 3520 2857 Mozilla/2.0b5 (W 696E 3935 3B20 4929 * 0D0A 486F 7374 3A20 in95; I)~~Host: 3839 2E31 372E 3130 * 2E31 0D0A 4163 6365 89.17.10.1~~Acce 7074 3A20 696D 6167 * 652F 6769 662C 2069 pt: image/gif, i 6D61 6765 2F78 2D78 * 6269 746D 6170 2C20 mage/x-xbitmap, 696D 6167 652F 6A70 * 6567 2C20 696D 6167 image/jpeg, imag 652F 706A 7065 672C * 202A 2F2A 0D0A 0D0A e/pjpeg, */*~~~~ 10:20:40.66 SMABSZ16.http > pcd72097.1055: . ack 233 win 32767 4500 0028 BCA7 0000 * 4006 9DC6 5911 0A01 E~~(<'~~@~~FY~~~ 5911 643F 0050 041F * 0056 1202 007C 88FD Y~d?~P~~~V~~~|~} 5010 7FFF 6F32 0000 * 0000 5491 C000 P~~o2~~~~T~@~ 10:20:40.74 SMABSZ16.http > pcd72097.1055: F 1:1(0) ack 233 win 32767 4500 0028 BCA8 0000 * 4006 9DC5 5911 0A01 E~~(<(~~@~~EY~~~ 5911 643F 0050 041F * 0056 1202 007C 88FD Y~d?~P~~~V~~~|~} 5011 7FFF 6F31 0000 * 0000 0008 0000 P~~o1~~~~~~~~ 10:20:40.74 pcd72097.1055 > SMABSZ16.http: . ack 2 win 8760 (DF) 4500 0028 9507 4000 * 2006 A566 5911 643F E~~(~~@~ ~%fY~d? 5911 0A01 041F 0050 * 007C 88FD 0056 1203 Y~~~~~~P~|~}~V~~ 5010 2238 CCF8 0000 * 0000 0000 0000 P~"8Lx~~~~~~~~ 10:20:40.77 pcd72097.1055 > SMABSZ16.http: R 8161533:8161533(0) win 0 (DF) 4500 0028 9807 4000 * 2006 A266 5911 643F E~~(~~@~ ~"fY~d? 5911 0A01 041F 0050 * 007C 88FD 44BD 3069 Y~~~~~~P~|~}D=0i 5004 0000 8C6F 0000 * 0000 0000 0000 P~~~~o~~~~~~~~ --- note long delay here. Maybe user delay? I suspect that something in the exchange above has caused the requestor to report the error. 10:21:04.74 pcd72097.1056 > SMABSZ16.http: S 8185492:8185492(0) win 8192 <mss 1460> (DF) 4500 002C 9C07 4000 * 2006 9E62 5911 643F E~~,~~@~ ~~bY~d? 5911 0A01 0420 0050 * 007C E694 0000 0000 Y~~~~ ~P~|f~~~~~ 6002 2000 6C43 0000 * 0204 05B4 B4B4 `~ ~lC~~~~~444 Greg
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