Hey everyone! I recently switched from netcat to ncat because of its extra features, and I've set up a basic server that executes a script for every client connection. The command I'm using is `ncat -l 5000 -k -e 'server_script'`. The script simply reads a line of input and echoes it back. The connection works well, but here's my issue: after entering a line on the client side, the connection doesn't close automatically as I expected. I want the server to disconnect the client immediately after the script finishes executing, but it seems like it waits for another input before closing. What can I do to ensure the connection closes right after the server script ends? Thanks!
3 Answers
What happens if your server script only echoes text without reading any input? Also, try checking the process table to see if the script is still held in memory when you're running into this issue. It could provide some insight into why the connection isn't terminating as it should.
The connection shouldn't close right after the script ends because TCP connections require both ends to agree on the closure. When your script finishes, it's not indicating to the client that it has no more data to send. A workaround is to use Ctrl-D on the client side to signal EOF, which should terminate the connection properly. Ncat is designed to be a more generic tool than telnet and thus doesn't close automatically like some other clients would when the server sends the final data. You might consider trying out socat, which handles this scenario in a more straightforward way by closing the connection when the server stops sending data.
That makes sense. I think switching to socat might actually help you out since it's designed to handle those situations more intuitively.
Have you checked the input method of your client? Sometimes extra characters like Ctrl-M or Ctrl-J can keep the connection open unexpectedly. Make sure to test both to see if they affect the connection's closure. Also, running the script directly in the shell works as expected, so the issue seems tied to how ncat manages the connection after running the script.
Good point! If the script runs fine in the shell, it really seems like something specific to ncat's behavior.
Agreed, the difference in handling end-of-line characters could definitely be a factor.
Yeah, I'm with you on this. If socat resolves the problem, it could save you a lot of hassle.