Test whether ZMQ_ROUTER sockets grow as peers connect and disconnect. It looks like they don't. To run, download all three files into the same directory and run: sh disconnect_test.sh

connect_die.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <zmq.h>

#define zcheck_err(eval, condition, fmt, args...)                                                                     \
((void)({                                                                                                             \
    errno = 0;                                                                                                        \
    if (!(condition)) {                                                                                               \
        fprintf(stderr, "%s: " fmt "%s%s\n", prog_name, ##args, errno ? ": " : "", errno ? zmq_strerror(errno) : ""); \
        exit(eval);                                                                                                   \
    }                                                                                                                 \
}))

char *prog_name;

/*
 * Connect to a socket, send a single empty message, exit.
 *
 * comment out zmq_close() and zmq_ctx_destory() to simulate dirty disconnect
 * must then uncomment zmq_recvmsg() otherwise we die before the message makes it to the wire
 */
int main(int argc, char **argv)
{
	void     *ctx, *soc;
	zmq_msg_t msg;

	prog_name = argv[0];

	zcheck_err(EXIT_FAILURE,   2 <= argc                       , "Supply endpoint then ID as arguments");
	zcheck_err(EXIT_FAILURE, ctx  = zmq_ctx_new()              , "Error creating context"              );
	zcheck_err(EXIT_FAILURE, soc  = zmq_socket(ctx, ZMQ_DEALER), "Error creating socket"               );

	if (argc == 3)
		zcheck_err(EXIT_FAILURE, 0 == zmq_setsockopt(soc, ZMQ_IDENTITY, argv[2], strlen(argv[2])), "Error identifying as %s", argv[2]);

	zcheck_err(EXIT_FAILURE,  0 == zmq_connect(soc, argv[1]), "Error connecting to endpoint %s", argv[1]);
	zcheck_err(EXIT_FAILURE,  0 == zmq_msg_init(&msg)       , "Error initialising message"              );
	zcheck_err(EXIT_FAILURE, -1 != zmq_sendmsg(soc, &msg, 0), "Error sending message"                   );
	zcheck_err(EXIT_FAILURE,  0 == zmq_close(soc)           , "Error closing socket"                    );
	zcheck_err(EXIT_FAILURE,  0 == zmq_ctx_destroy(ctx)     , "Error destroying context"                );
//	zcheck_err(EXIT_FAILURE, -1 != zmq_recvmsg(soc, &msg, 0), "Error receiving ack"                     );

	return 0;
}

disconnect_test.sh

#!/bin/sh
#
# Create a ZMQ_ROUTER, bind to $BIND, echo messages
# Output PID of router so you may monitor the process
# Continually connect to $CONNECT, send a message, then die
# Print relevant memory information for router (recommend a wide terminal)
#
# Should work with any sh, went through and got rid of bashisms

trap die INT TERM
die() {
	[ -n "$router_pid" ] && kill $router_pid
	printf "$0: $@\n" 1>&2
	exit
}

BIND="tcp://lo:12345"
CONNECT="tcp://localhost:12345"

gcc -lzmq -Wall -Wextra -Werror -o router_echo router_echo.c || die "Could not compile router_echo.c"
gcc -lzmq -Wall -Wextra -Werror -o connect_die connect_die.c || die "Could not compile connect_die.c"

./router_echo "$BIND" &
router_pid=$!

ps $router_pid > /dev/null 2>&1 || die "Error starting router_echo"

echo "Router pid is $router_pid. Press [Enter] to continue."
read unused

unset i
while true; do
	i=$((i + 1))
	./connect_die "$CONNECT" client_$i || die "Error starting a client"
	egrep "Vm" /proc/$router_pid/status | sed ':l; N; $!bl; s/[\n\t ]\+/ /g;'
done

wait

router_echo.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <zmq.h>

#define zcheck_err(eval, condition, fmt, args...)                                                                     \
((void)({                                                                                                             \
    errno = 0;                                                                                                        \
    if (!(condition)) {                                                                                               \
        fprintf(stderr, "%s: " fmt "%s%s\n", prog_name, ##args, errno ? ": " : "", errno ? zmq_strerror(errno) : ""); \
        exit(eval);                                                                                                   \
    }                                                                                                                 \
}))

char *prog_name;

/*
 * Create ZMQ_ROUTER socket, bind, echo messages.
 */
int main(int argc, char **argv)
{
	int       con;
	void     *ctx, *soc;
	zmq_msg_t msg;

	prog_name = argv[0];

	zcheck_err(EXIT_FAILURE,   2 == argc                       , "Supply endpoint as only argument"     );
	zcheck_err(EXIT_FAILURE, ctx  = zmq_ctx_new()              , "Error creating context"               );
	zcheck_err(EXIT_FAILURE, soc  = zmq_socket(ctx, ZMQ_ROUTER), "Error creating socket"                );
	zcheck_err(EXIT_FAILURE,   0 == zmq_bind(soc, argv[1])     , "Error binding to endpoint %s", argv[1]);
	zcheck_err(EXIT_FAILURE,   0 == zmq_msg_init(&msg)         , "Error initialise mesage"              );

	setbuf(stdout, NULL);
	for (con = 0;;) {
		int    more;
		size_t size = sizeof(more);
		zcheck_err(EXIT_FAILURE, -1 != zmq_recvmsg(soc, &msg, 0)                     , "Error receiving message"       );
		zcheck_err(EXIT_FAILURE,  0 == zmq_getsockopt(soc, ZMQ_RCVMORE, &more, &size), "Error checking for ZMQ_RCVMORE");
		zcheck_err(EXIT_FAILURE, -1 != zmq_sendmsg(soc, &msg, more ? ZMQ_SNDMORE : 0), "Error echoing message"         );
		if (!more)
			printf("Received: %d ", ++con);
	}

	return 0;
}