java-sctp

Short example that uses SCTP in Java. I used the code from Oracle's SCTP example.

Ubuntu

For a first test, I used a Ubuntu 17.10 64 Bit VM, since OpenJDK officially supports SCTP on Linux. I installed OpenJDK and a required libsctp packet.

$ sudo apt install openjdk-8-jdk
$ sudo apt install libsctp-dev

Now I could compile and run the example (see ubuntu.pcap for a network packet trace).

$ javac DaytimeClient.java DaytimeServer.java 
$ java DaytimeServer &
$ java DaytimeClient
New association setup with 10 outbound streams, and 10 inbound streams.
(US) 10:16:26 AM Thu 15 Mar 18, Central European Time
(FR) 10:16:26 AM jeu. 15 mars 18, Heure d'Europe centrale
The association has been shutdown.

I did not added SCTP support to the Ubuntu kernel. However, after I started the DaytimeServer, Ubuntu has automatically loaded the SCTP Kernel module.

$ cat /proc/modules | grep sctp
sctp 299008 7 - Live 0x0000000000000000
libcrc32c 16384 1 sctp, Live 0x0000000000000000

FreeBSD

For my next test, I used a FreeBSD 12.0-CURRENT amd64 VM. As with Ubuntu, I installed OpenJDK and compiled the code.

% sudo pkg install openjdk8
% javac DaytimeClient.java DaytimeServer.java 

Unfortunately, running the example on FreeBSD was not that successful (see freebsd.pcap for a network packet trace).

% java DaytimeServer &
[1] 2281
% java DaytimeClient
Exception in thread "main" New association setup with 10 outbound streams, and 10 inbound streams.
java.net.SocketException: Invalid argument
	at sun.nio.ch.sctp.SctpChannelImpl.send0(Native Method)
	at sun.nio.ch.sctp.SctpChannelImpl.sendFromNativeBuffer(SctpChannelImpl.java:1045)
	at sun.nio.ch.sctp.SctpChannelImpl.send(SctpChannelImpl.java:997)
	at sun.nio.ch.sctp.SctpChannelImpl.send(SctpChannelImpl.java:977)
	at DaytimeServer.main(DaytimeServer.java:41)
Exception in thread "main" java.net.SocketException: Connection reset by peer
	at sun.nio.ch.sctp.SctpChannelImpl.receive0(Native Method)
	at sun.nio.ch.sctp.SctpChannelImpl.receiveIntoNativeBuffer(SctpChannelImpl.java:859)
	at sun.nio.ch.sctp.SctpChannelImpl.receive(SctpChannelImpl.java:835)
	at sun.nio.ch.sctp.SctpChannelImpl.receive(SctpChannelImpl.java:778)
	at sun.nio.ch.sctp.SctpChannelImpl.receive(SctpChannelImpl.java:740)
	at DaytimeClient.main(DaytimeClient.java:27)

The truss utility revealed that the Invalid argument error comes from sendmsg.

% truss java DaytimeServer &
% java DaytimeClient
...
sendmsg(7,0x7fffdfffd600,0)			 ERR#22 'Invalid argument'
...

Since OpenJDK seems to do not support SCTP on FreeBSD, this is somehow OK. However, I further investigate this issue. In the sendmsg call, a buffer address and a buffer length 0 is passed. This is OK for Linux, but it is an invalid argument for FreeBSD (buffer address needs to be NULL, if buffer length is 0). In OpenJDK8, I found the code lines in function Java_sun_nio_ch_sctp_SctpChannelImpl_send0 of

jdk/src/solaris/native/sun/nio/ch/sctp/SctpChannelImpl.c

In this file I found two ifdef OS statements that I fixed for FreeBSD as well. I created the patch file patch-jdk-src-solaris-native-sun-nio-ch-sctp-SctpChannelImpl.c and used the FreeBSD ports collection to install OpenJDK8 with this patch.

% sudo pkg remove openjdk8
% sudo cp patch-jdk-src-solaris-native-sun-nio-ch-sctp-SctpChannelImpl.c /usr/ports/java/openjdk8/files
% cd /usr/ports/java/openjdk8
% sudo make install

After that I recompiled my java test files and run it again (see freebsd-patched.pcap for a network packet trace).

$ javac DaytimeClient.java DaytimeServer.java 
$ java DaytimeServer &
$ java DaytimeClient
New association setup with 10 outbound streams, and 10 inbound streams.
(US) 2:56:42 PM Tue 31 Jul 18, Central European Summer Time
(FR) 2:56:42 PM mar. 31 juil. 18, Heure d'?t? d'Europe centrale
The association has been shutdown.