Post by Denys VlasenkoPost by Rob LandleyPost by Chuck KueckerHello,
This might be a simple problem, but so far I've not found a good solution.
I am running Busybox in an ARM embedded system. I want to be able to
transfer a file from the embedded device to my Linux host. The host
system has tftp working - that's how I load the ARM system files.
I issue tftp -p -l /mjpeg.api 192.168.0.200 69 at the embedded system
tftp: server error: (2) Access violation
What does this mean. and what should I look at to fix it?
Add an ssh client to your box?
http://impactlinux.com/fwl/downloads/binaries
Alternately, if you're asking what you can do with busybox, I'd suggest
ftpget and ftpput to an ftpd on the host. (The tftp protocol is kind of
sat, use real ftp.)
But busybox ftpd requires an inetd variant to run under, and the easy way
$ netcat -l -p 12345 -e cat bigfile &
$ telnet 127.0.0.1 12345 > outfile
127.0.0.1: Connection reset by peer
Connection closed by foreign host.
$ ls -l bigfile outfile
-rw-r--r-- 1 landley landley 22940512 2010-04-26 23:51 bigfile
-rw-r--r-- 1 landley landley 20775272 2010-04-26 23:54 outfile
That's a basic sanity test this implementation isn't passing.
How did you manage to run busybox nc as "netcat"?
Please show "netcat --help" output.
My bad. I screwed up twice here:
1) I hand-edited
landley at driftwood:~$ ~/firmware/firmware/build/host/busybox nc -l -p 12345 -e
cat glibc-2.7.tar.bz2
Into a more readable command line, and screwed it up when I did so. (It was
nc. In toybox netcat is a synonym for nc, in busybox it isn't but I was
testing the busybox one.)
2) I also didn't want to use netecat as both the sending and receiving
program, so I could tell which half of the transaction was causing which
behavior. I forgot the telnet escape sequence stuff happens even when it
doesn't get a controlling TTY.
Post by Denys VlasenkoWhy do you think telnet is a good method for downloading
raw binary data? It mangles 0xff bytes, for one.
It tries to respond to TELOPT_TTYPE options (255,24 byte pairs)
by sending back $TERM value. If it happens enough times,
network pipe fills up (since cat doesn't read stdin in this case),
and everything stalls.
Yeah, that's probably what happened here. Again, my bad.
Post by Denys VlasenkoPost by Rob LandleyI used to have this working, but git commit 29fe7265b8c1917ebc blew away
my code with a completely unrelated external port that doesn't even get
the basic bidirectional shutdown() stuff right.
Clue me in what is this shutdown() thing.
man 2 shutdown. It closes down one half of a connection, so that when the
other end reads from a pipe they get EOF, but can still write to it. (Or vice
versa.)
The first version of netcat I messed with (circa 2001) wasn't doing shutdown
handling at all, and thus something like:
echo "GET /" | netcat www.cnn.com 80
Wouldn't work, because as soon as netcat saw the end of input, it would
close(fd) the network connection and thus no longer be able to receive any
data from the remote server. But if it just ignored it the result would be a
hang instead because the remote server won't start sending data back in that
case unless it reads EOF from the socket because otherwise it'll sit there
waiting for HTTP 1.1 headers when it's only going to get HTTP 1.0. (It's a
funky corner case. There's a lot of those.)
Apparently the "upstream" netcat has since been fixed, and the bug I was
hitting was actually due to the behavior of Ubuntu's telnet. Sorry about
that.
Post by Denys VlasenkoPost by Rob LandleyIt also doesn't have things like the
persistent server option (-L), or the ability to allocate a tty (-t), or
the connect to file option (netcat -f) which let netcat attach stdin and
stdout to an arbitrary char device (such as /dev/ttyS0) instead of a
network socket. (I was kind of proud of that one.)
Every new reimplementation of nc adds more features. Yours is actually
better than most, because others don't bother to not *break compatibility*.
So to get these features put back into busybox I'd have to get them into an
"upstream" project?
In toybox -l -L -t are under the config symbol NETCAT_LISTEN, to provide server
options. Possibly I should probably move -f into there too, but I don't
really bang on that much anymore...
Rob
--
Latency is more important than throughput. It's that simple. - Linus Torvalds