netcat (/usr/bin/nc) buffer size too small - alternate utilities?

Adam Vande More amvandemore at
Tue Feb 16 20:13:59 UTC 2010

On Tue, Feb 16, 2010 at 1:42 PM, Nerius Landys <nlandys at> wrote:

> I'm communicating with a server that uses UDP packets.  The server
> receives a UDP packet, and responds with a UDP packet by sending one
> to the initial sender.  The request packets are always very small in
> size, but the response UDP packets can be up to 9216 bytes in size.
> I am using netcat like so:
> echo "$REQUEST_BODY" | /usr/bin/nc -w 1 -u "$PLAYERDB_HOST"
> The response always gets truncated to 1024 bytes using netcat.
> I wrote my own silly version of netcat specifically suited to my needs
> over UDP, in Java. I then call it like so:
> echo "$REQUEST_BODY" | /usr/local/bin/java SendUDP "$PLAYERDB_HOST"
> (Source code at the end of this message.)
> With my Java program, I'm able to get up to 9216 bytes in my UDP
> response packet; the response won't be truncated to 1024 bytes like in
> netcat.
> Now I've read the netcat manpage and it says nothing about any buffer
> size or ways to increase it.  I don't really want to use my Java
> program because starting up a JVM for each server query is very
> expensive.  Any ideas of any other tools like netcat that will enable
> me to receive UDP packets up to 9216 bytes in size?

You can try raising OS's UDP buff size:

sysctl kern.ipc.maxsockbuf=8388608

or write an equivalent app in python...

Adam Vande More

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