Sending test data from a file to port and IP

tnine9 · 04-23-2009, 12:07 AM

Hi all,
I'm working on testing some software, and I have a question. We have several files of binary data that we need to push through our application to test. It communicates via simple TCP sockets. Is there a way I can send this data to the socket from the command line? I tried doing something like this, but telnet never picked up the data.

Code:

telnet localhost 81 << cat inputtest1.sbd

Thanks,
Todd

anomie · 04-23-2009, 12:10 AM

Use netcat for this. (See the manpages for nc(1).)

---

edit: Here is a little example -

Code:

$ cat /etc/passwd | nc 127.0.0.1 6969

(In my case I set up a listener on tcp 6969.)

tnine9 · 04-23-2009, 10:21 PM

Thanks for the help, but I'm getting some wierd errors. My test message is only 28 bytes in length, but when my program receives it I have as 8192 bytes on the buffer coming from the sender. I've tried both

Code:

cat test.sbd |nc localhost 8080

and

Code:

nc localhost 8080 < test.sbd

I've noticed that it sends the data, but it doesn't disconnect from the socket after the data is sent. Is there a param I'm missing? I couldn't find anything in the man pages but I need to set the socket buffer length to match the number of bytes in the message. I know this isn't a bug in the receiver given that the production system only transmits the size of the input file then closes the socket, and the receiver has the correct buffer length.

Thanks,
Todd

anomie · 04-23-2009, 10:46 PM

Without knowing anything about the application you're testing, I am not sure what to suggest on that front. To troubleshoot further, you may want to capture the packets and see what is going on with the tcp conversation.

# tcpdump -i lo tcp port 8080

jschiwal · 04-24-2009, 12:35 AM

On some kernels & bash versions, you can use /dev/tcp/<host>/<port> and /dev/tcp/<host>/<port> as a device that you can cat to or from.

See the bash info manual. Section 3.6 Redirections

tnine9 · 04-27-2009, 04:06 PM

Well, both solutions work for pushing data through a socket. However I'm still experiencing the issues of an invalid length. I'm actually running OS X 10.5, so it must be an issue with it's network sockets. I've tried both cat and dd to dump the bytes onto the pipe for the network calls, but it doesn't seem to help the issue. It looks like I'm going to have to write something that disconnects after sending the bytes in the file.