Rewrite of https://gist.github.com/deepcube/5417288 in czmq. To run download all files in a directory and run: sh czmq_disconnect_test.sh

czmq_connect_die.c

#include <czmq.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;

/*
 * Connect to a socket, send a single empty message, exit.
 */
int main(int argc, char **argv)
{
	zctx_t *ctx;
	void   *soc;
	zmsg_t *msg;

	prog_name = argv[0];

	zcheck_err(EXIT_FAILURE, argc <= 3                           , "Supply endpoint then ID as arguments");
	zcheck_err(EXIT_FAILURE, ctx   = zctx_new()                  , "Error creating context"              );
	zcheck_err(EXIT_FAILURE, soc   = zsocket_new(ctx, ZMQ_DEALER), "Error creating socket"               );

	if (argc == 3)
		zsocket_set_identity(soc, argv[2]);

	zcheck_err(EXIT_FAILURE,    0 <= zsocket_connect(soc, argv[1]), "Error connecting to %s", argv[1]);
	zcheck_err(EXIT_FAILURE, msg   = zmsg_new()                   , "Error creating message"         );
	zcheck_err(EXIT_FAILURE,    0 == zmsg_pushmem(msg, "", 0)     , "Error adding empty frame"       );
	zcheck_err(EXIT_FAILURE,    0 == zmsg_send(&msg, soc)         , "Error sending message"          );
	zcheck_err(EXIT_FAILURE, msg   = zmsg_recv(soc)               , "Error receiving message"        );
//	zctx_destroy(&ctx);

	return 0;
}

czmq_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 -lczmq -Wall -Werror -o czmq_router_echo czmq_router_echo.c || die "Error compiling czmq_router_echo.c"
gcc -lzmq -lczmq -Wall -Werror -o czmq_connect_die czmq_connect_die.c || die "Error compiling czmq_connect_die.c"

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

wait

czmq_router_echo.c

#include <czmq.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;

int echo(zloop_t *loop, zmq_pollitem_t *item, void *arg)
{
	zmsg_t    *msg;
	static int con = 0;

	zcheck_err(EXIT_FAILURE, msg  = zmsg_recv(item->socket)      , "Error receiving message");
	zcheck_err(EXIT_FAILURE,   0 == zmsg_send(&msg, item->socket), "Error sending message"  );
	printf("Received: %d ", ++con);

	return 0;
}

/*
 * Create ZMQ_ROUTER socket, bind, echo messages.
 */
int main(int argc, char **argv)
{
	zctx_t         *ctx;
	void           *soc;
	zloop_t        *loop;
	zmq_pollitem_t  poller;

	prog_name = argv[0];

	zcheck_err(EXIT_FAILURE, argc == 2                           , "Supply endpoint as only argument"   );
	zcheck_err(EXIT_FAILURE, ctx   = zctx_new()                  , "Error creating context"             );
	zcheck_err(EXIT_FAILURE, soc   = zsocket_new(ctx, ZMQ_ROUTER), "Error creating socket"              );
	zcheck_err(EXIT_FAILURE,    0 <= zsocket_bind(soc, argv[1])  , "Error binding socket to %s", argv[1]);
	zcheck_err(EXIT_FAILURE, loop  = zloop_new()                 , "Error creating zloop"               );

	poller = (zmq_pollitem_t){ .socket = soc, .fd = 0, .events = ZMQ_POLLIN, .revents = 0 };

	zcheck_err(EXIT_FAILURE, 0 == zloop_poller(loop, &poller, echo, NULL), "Error registering poller");

	setbuf(stdout, NULL);
	zloop_start(loop);

	return 0;
}