How do I interactively type \r\n-terminated query in netcat?

Question

$ nc example.com 80
GET / HTTP/1.1
Host: example.com 

HTTP/1.1 200 OK
...

It works, line separator is just 0A here instead of required 0D0A.

How do I type a 0D0A-separated query in netcat?

It is easy to do one-time thing with printf manually typing \r\n each time or to implement some todos-like Perl oneliner and pipe it to nc, but maybe there is some easy way I miss?

score 34 · Accepted Answer · answered Jul 18 '15 at 11:30

34

My netcat has an option -C or --crlf to replace \n by \r\n on stdin.

Alternatively, it depends on what terminal you are using. My default settings can be seen by:

$ stty -a
... lnext = ^V; ...

This shows the literal-next character for input is control-V. So typing control-v followed by control-m will insert a carriage-return (as opposed to a newline, which is what you get when you hit the return or enter key).

answered Jul 18 '15 at 11:30

meuh

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Nice find, didn't know about `-C`. – cYrus Jul 18 '15 at 11:34
What about sending any byte interactively through netcat, e.g. `0x01`, `0x02`, etc. Is it possible?. – Jaime Hablutzel Jan 10 '18 at 18:16
1

This option doesn't seem to be supported on GNU Netcat – Codebling Oct 12 '19 at 16:19
@CodeBling You can also try socat if you have that: `socat READLINE TCP4:example.com:80,crnl` – meuh Oct 12 '19 at 17:53
@meuh good call – Codebling Oct 12 '19 at 19:02

score 3 · Answer 2 · answered Jul 18 '15 at 11:09

3

You can pipe a string to nc:

echo -ne 'GET / HTTP/1.1\r\nHost: example.com\r\n\r\n' | nc example.com 80

Check with:

$ echo -ne 'GET / HTTP/1.1\r\nHost: example.com\r\n\r\n' | hd
00000000  47 45 54 20 2f 20 48 54  54 50 2f 31 2e 31 0d 0a  |GET / HTTP/1.1..|
00000010  48 6f 73 74 3a 20 65 78  61 6d 70 6c 65 2e 63 6f  |Host: example.co|
00000020  6d 0d 0a 0d 0a                                    |m....|
00000025

answered Jul 18 '15 at 11:09

cYrus

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How do I do this interactively, entering another request after I see the reply? – Vi. Jul 18 '15 at 11:20

How do I interactively type \r\n-terminated query in netcat?

2 Answers2