This is a TCP/IP debugger/proxy allowing to intercept the network traffic. It can serve multiple connections in parallel.
This program is written in Go and requires at least the release 1.
For example:
go run gotcpspy.go -host=ftp.idsoftware.com -port 21 -listen_port=8081
It starts running with the message:
Start listening on port 8081 and forwarding data to ftp.idsoftware.com:21
In a separate console you can run:
telnet localhost 8081
and enter something, for example, USER test <ENTER>,
PASS test@test.org <ENTER> and finally QUIT <ENTER>.
It should produce three logs.
log-2012.04.20-12.10.12-0001-10.44.2.21-26311-192.246.40.185-21.log
Connected to ftp.idsoftware.com:21 at 2012.04.20-12.10.12
Received (#0, 00000000) 24 bytes from 10.44.2.21-26311
00000000 32 32 30 2d 66 74 70 2e 69 64 73 6f 66 74 77 61 |220-ftp.idsoftwa|
00000010 72 65 2e 63 6f 6d 0d 0a |re.com..|
Sent (#0) to 127.0.0.1-8081
Received (#1, 00000018) 353 bytes from 10.44.2.21-26311
00000000 32 32 30 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |220-------------|
00000010 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
00000020 2d 0d 0a 32 32 30 2d 57 65 6c 63 6f 6d 65 20 74 |-..220-Welcome t|
00000030 6f 20 66 74 70 2e 69 64 73 6f 66 74 77 61 72 65 |o ftp.idsoftware|
00000040 2e 63 6f 6d 0d 0a 32 32 30 2d 2d 2d 2d 2d 2d 2d |.com..220-------|
00000050 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
00000060 2d 2d 2d 2d 2d 2d 2d 0d 0a 32 32 30 2d 0d 0a 32 |-------..220-..2|
00000070 32 30 2d 43 6f 6e 6e 65 63 74 69 6f 6e 20 66 72 |20-Connection fr|
00000080 6f 6d 20 38 30 2e 31 36 39 2e 33 34 2e 31 39 34 |om 80.169.34.194|
00000090 20 6c 6f 67 67 65 64 0d 0a 32 32 30 2d 59 6f 75 | logged..220-You|
000000a0 20 61 72 65 20 75 73 65 72 20 32 30 20 6f 66 20 | are user 20 of |
000000b0 31 35 30 20 61 76 61 69 6c 61 62 6c 65 20 63 6f |150 available co|
000000c0 6e 6e 65 63 74 69 6f 6e 73 2e 0d 0a 32 32 30 2d |nnections...220-|
000000d0 0d 0a 32 32 30 2d 41 76 65 72 61 67 65 20 74 68 |..220-Average th|
000000e0 72 6f 75 67 68 70 75 74 20 66 6f 72 20 74 68 69 |roughput for thi|
000000f0 73 20 73 65 72 76 65 72 20 69 73 20 32 34 38 2e |s server is 248.|
00000100 38 38 37 20 4b 42 70 73 2e 0d 0a 32 32 30 2d 35 |887 KBps...220-5|
00000110 35 37 34 20 70 65 6f 70 6c 65 20 68 61 76 65 20 |574 people have |
00000120 76 69 73 69 74 65 64 20 74 68 69 73 20 73 69 74 |visited this sit|
00000130 65 20 69 6e 20 74 68 65 20 6c 61 73 74 20 32 34 |e in the last 24|
00000140 20 68 6f 75 72 73 2e 0d 0a 32 32 30 2d 0d 0a 32 | hours...220-..2|
00000150 32 30 2d 0d 0a 32 32 30 2d 0d 0a 32 32 30 20 0d |20-..220-..220 .|
00000160 0a |.|
Sent (#1) to 127.0.0.1-8081
Received (#0, 00000000) 1 bytes from 127.0.0.1-8081
00000000 55 |U|
Sent (#0) to 10.44.2.21-26311
Received (#1, 00000001) 1 bytes from 127.0.0.1-8081
00000000 53 |S|
Sent (#1) to 10.44.2.21-26311
Received (#2, 00000002) 10 bytes from 127.0.0.1-8081
00000000 45 52 20 61 6e 6f 6e 79 6d 6f |ER anonymo|
Sent (#2) to 10.44.2.21-26311
Received (#3, 0000000C) 2 bytes from 127.0.0.1-8081
00000000 75 73 |us|
Sent (#3) to 10.44.2.21-26311
Received (#4, 0000000E) 2 bytes from 127.0.0.1-8081
00000000 0d 0a |..|
Sent (#4) to 10.44.2.21-26311
Received (#2, 00000179) 70 bytes from 10.44.2.21-26311
00000000 33 33 31 20 55 73 65 72 20 6e 61 6d 65 20 6f 6b |331 User name ok|
00000010 61 79 2c 20 70 6c 65 61 73 65 20 73 65 6e 64 20 |ay, please send |
00000020 63 6f 6d 70 6c 65 74 65 20 45 2d 6d 61 69 6c 20 |complete E-mail |
00000030 61 64 64 72 65 73 73 20 61 73 20 70 61 73 73 77 |address as passw|
00000040 6f 72 64 2e 0d 0a |ord...|
Sent (#2) to 127.0.0.1-8081
Received (#5, 00000010) 1 bytes from 127.0.0.1-8081
00000000 50 |P|
Sent (#5) to 10.44.2.21-26311
Received (#6, 00000011) 3 bytes from 127.0.0.1-8081
00000000 41 53 53 |ASS|
Sent (#6) to 10.44.2.21-26311
Received (#7, 00000014) 2 bytes from 127.0.0.1-8081
00000000 20 74 | t|
Sent (#7) to 10.44.2.21-26311
Received (#8, 00000016) 1 bytes from 127.0.0.1-8081
00000000 65 |e|
Sent (#8) to 10.44.2.21-26311
Received (#9, 00000017) 1 bytes from 127.0.0.1-8081
00000000 73 |s|
Sent (#9) to 10.44.2.21-26311
Received (#10, 00000018) 2 bytes from 127.0.0.1-8081
00000000 74 40 |t@|
Sent (#10) to 10.44.2.21-26311
Received (#11, 0000001A) 6 bytes from 127.0.0.1-8081
00000000 6e 61 6d 65 2e 6f |name.o|
Sent (#11) to 10.44.2.21-26311
Received (#12, 00000020) 2 bytes from 127.0.0.1-8081
00000000 72 67 |rg|
Sent (#12) to 10.44.2.21-26311
Received (#13, 00000022) 2 bytes from 127.0.0.1-8081
00000000 0d 0a |..|
Sent (#13) to 10.44.2.21-26311
Received (#3, 000001BF) 30 bytes from 10.44.2.21-26311
00000000 32 33 30 20 55 73 65 72 20 6c 6f 67 67 65 64 20 |230 User logged |
00000010 69 6e 2c 20 70 72 6f 63 65 65 64 2e 0d 0a |in, proceed...|
Sent (#3) to 127.0.0.1-8081
Received (#14, 00000024) 1 bytes from 127.0.0.1-8081
00000000 51 |Q|
Sent (#14) to 10.44.2.21-26311
Received (#15, 00000025) 3 bytes from 127.0.0.1-8081
00000000 55 49 54 |UIT|
Sent (#15) to 10.44.2.21-26311
Received (#16, 00000028) 2 bytes from 127.0.0.1-8081
00000000 0d 0a |..|
Sent (#16) to 10.44.2.21-26311
Received (#4, 000001DD) 14 bytes from 10.44.2.21-26311
00000000 32 32 31 20 47 6f 6f 64 62 79 65 21 0d 0a |221 Goodbye!..|
Sent (#4) to 127.0.0.1-8081
Disconnected from 10.44.2.21-26311
Disconnected from 127.0.0.1-8081
Finished at 2012.04.20-12.10.12, duration 16.5769481s
log-binary-2012.04.20-12.10.12-0001-10.44.2.21-26311.log
USER anonymous
PASS test@name.org
QUIT
log-binary-2012.04.20-12.10.12-0001-192.246.40.185-21.log
220-ftp.idsoftware.com
220------------------------------
220-Welcome to ftp.idsoftware.com
220------------------------------
220-
220-Connection from 80.169.34.194 logged
220-You are user 20 of 150 available connections.
220-
220-Average throughput for this server is 248.887 KBps.
220-5574 people have visited this site in the last 24 hours.
220-
220-
220-
220
331 User name okay, please send complete E-mail address as password.
230 User logged in, proceed.
221 Goodbye!