The error I'm getting is "java.io.IOException: Connection reset by peer" on the 1017th connection.

"lsof -n -p 6595" shows:

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME

stunnel 6595 ec2-user cwd DIR 202,1 4096 2 /

stunnel 6595 ec2-user rtd DIR 202,1 4096 2 /

stunnel 6595 ec2-user txt REG 202,1 2510282 8807 /usr/local/bin/stunnel

stunnel 6595 ec2-user mem REG 202,1 1903208 7619 /lib64/libc-2.12.so

stunnel 6595 ec2-user mem REG 202,1 138328 7643 /lib64/libpthread-2.12.so

stunnel 6595 ec2-user mem REG 202,1 113432 7629 /lib64/libnsl-2.12.so

stunnel 6595 ec2-user mem REG 202,1 14584 7651 /lib64/libutil-2.12.so

stunnel 6595 ec2-user mem REG 202,1 19536 7625 /lib64/libdl-2.12.so

stunnel 6595 ec2-user mem REG 202,1 154464 17671 /lib64/ld-2.12.so

stunnel 6595 ec2-user 0u CHR 1,3 0t0 19 /dev/null

stunnel 6595 ec2-user 1u CHR 1,3 0t0 19 /dev/null

stunnel 6595 ec2-user 2u CHR 1,3 0t0 19 /dev/null

stunnel 6595 ec2-user 4r FIFO 0,8 0t0 534916 pipe

stunnel 6595 ec2-user 5w FIFO 0,8 0t0 534916 pipe

stunnel 6595 ec2-user 6u unix 0xffff880001d26900 0t0 534919 socket

stunnel 6595 ec2-user 7u IPv4 534920 0t0 TCP *:commplex-link (LISTEN)

"cat /etc/security/limits.conf" shows:

# /etc/security/limits.conf

#Each line describes a limit for a user in the form:

#<domain> <type> <item> <value>

#Where:

#<domain> can be:

# - an user name

# - a group name, with @group syntax

# - the wildcard *, for default entry

# - the wildcard %, can be also used with %group syntax,

# for maxlogin limit

#<type> can have the two values:

# - "soft" for enforcing the soft limits

# - "hard" for enforcing hard limits

#<item> can be one of the following:

# - core - limits the core file size (KB)

# - data - max data size (KB)

# - fsize - maximum filesize (KB)

# - memlock - max locked-in-memory address space (KB)

# - nofile - max number of open files

# - rss - max resident set size (KB)

# - stack - max stack size (KB)

# - cpu - max CPU time (MIN)

# - nproc - max number of processes

# - as - address space limit (KB)

# - maxlogins - max number of logins for this user

# - maxsyslogins - max number of logins on the system

# - priority - the priority to run user process with

# - locks - max number of file locks the user can hold

# - sigpending - max number of pending signals

# - msgqueue - max memory used by POSIX message queues (bytes)

# - nice - max nice priority allowed to raise to values: [-20, 19]

# - rtprio - max realtime priority

#<domain> <type> <item> <value>

#* soft core 0

#* hard rss 10000

#@student hard nproc 20

#@faculty soft nproc 20

#@faculty hard nproc 50

#ftp hard nproc 0

#@student - maxlogins 4

* - nofile 999999

# End of file

I believe that these settings should all allow way more than 1016 connections.

Any other clues for me?