diff --git a/contrib/debug/Makefile b/contrib/debug/Makefile
index 74e7547..385e0d1 100644
--- a/contrib/debug/Makefile
+++ b/contrib/debug/Makefile
@@ -3,10 +3,15 @@
 CC       = gcc
 OPTIMIZE = -O2
 DEFINE   =
-OBJS     = flags
+OBJS     = flags poll
+
+all: $(OBJS)
 
 flags: flags.c
 	$(CC) $(OPTIMIZE) $(DEFINE) $(INCLUDE) -o $@ $^
 
+poll: poll.c
+	$(CC) $(OPTIMIZE) $(DEFINE) $(INCLUDE) -o $@ $^
+
 clean:
 	rm -f $(OBJS) *.[oas] *~
diff --git a/contrib/debug/poll.c b/contrib/debug/poll.c
new file mode 100644
index 0000000..b535c07
--- /dev/null
+++ b/contrib/debug/poll.c
@@ -0,0 +1,358 @@
+#define _GNU_SOURCE // for POLLRDHUP
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* for OSes which don't have it */
+#ifndef POLLRDHUP
+#define POLLRDHUP 0
+#endif
+
+int verbose = 0;
+int cmd = 0;
+int cmdstep = 0;
+int zero = 0;
+int one  = 1;
+int lfd = -1;
+int cfd = -1;
+int sfd = -1;
+struct sockaddr_in saddr, caddr;
+socklen_t salen, calen;
+
+void usage(const char *arg0)
+{
+	printf("Usage: %s [ arg [<action>[,...]] ] ...\n"
+	       "args:\n"
+	       "    -h            display this help\n"
+	       "    -v            verbose mode (shows ret values)\n"
+	       "    -c <actions>  perform <action> on client side socket\n"
+	       "    -s <actions>  perform <action> on server side socket\n"
+	       "    -l <actions>  perform <action> on listening socket\n"
+	       "\n"
+	       "actions for -c/-s/-l (multiple may be delimited by commas) :\n"
+	       "    acc           accept on listener, implicit before first -s\n"
+	       "    snd           send a few bytes of data\n"
+	       "    mor           send a few bytes of data with MSG_MORE\n"
+	       "    rcv           receive a few bytes of data\n"
+	       "    drn           drain: receive till zero\n"
+	       "    shr           SHUT_RD : shutdown read side\n"
+	       "    shw           SHUT_WR : shutdown write side\n"
+	       "    shb           SHUT_RDWR : shutdown both sides\n"
+	       "    lin           disable lingering on the socket\n"
+	       "    clo           close the file descriptor\n"
+	       "    pol           poll() for any event\n"
+	       "\n", arg0);
+}
+
+void die(const char *msg)
+{
+	if (msg)
+		fprintf(stderr, "%s\n", msg);
+	exit(1);
+}
+
+const char *get_errno(int ret)
+{
+	static char errmsg[100];
+
+	if (ret >= 0)
+		return "";
+
+	snprintf(errmsg, sizeof(errmsg), " (%s)", strerror(errno));
+	return errmsg;
+}
+
+void do_acc(int fd)
+{
+	int ret;
+
+	calen = sizeof(caddr);
+	ret = accept(lfd, (struct sockaddr*)&caddr, &calen);
+	if (sfd < 0)
+		sfd = ret;
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_snd(int fd)
+{
+	int ret;
+
+	ret = send(fd, "foo", 3, MSG_NOSIGNAL|MSG_DONTWAIT);
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_mor(int fd)
+{
+	int ret;
+
+	ret = send(fd, "foo", 3, MSG_NOSIGNAL|MSG_DONTWAIT|MSG_MORE);
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_rcv(int fd)
+{
+	char buf[10];
+	int ret;
+
+	ret = recv(fd, buf, sizeof(buf), MSG_DONTWAIT);
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_drn(int fd)
+{
+	char buf[16384];
+	int total = -1;
+	int ret;
+
+	while (1) {
+		ret = recv(fd, buf, sizeof(buf), 0);
+		if (ret <= 0)
+			break;
+		if (total < 0)
+			total = 0;
+		total += ret;
+	}
+
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, total, get_errno(ret));
+}
+
+void do_shr(int fd)
+{
+	int ret;
+
+	ret = shutdown(fd, SHUT_RD);
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_shw(int fd)
+{
+	int ret;
+
+	ret = shutdown(fd, SHUT_WR);
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_shb(int fd)
+{
+	int ret;
+
+	ret = shutdown(fd, SHUT_RDWR);
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_lin(int fd)
+{
+	struct linger nolinger = { .l_onoff = 1, .l_linger = 0 };
+	int ret;
+
+	ret = setsockopt(fd, SOL_SOCKET, SO_LINGER, &nolinger, sizeof(nolinger));
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_clo(int fd)
+{
+	int ret;
+
+	ret = close(fd);
+	if (verbose)
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s\n", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret));
+}
+
+void do_pol(int fd)
+{
+	struct pollfd fds = { .fd = fd, .events = POLLIN|POLLOUT|POLLRDHUP, .revents=0 };
+	int ret;
+
+	ret = poll(&fds, 1, 0);
+	if (verbose) {
+		printf("cmd #%d stp #%d: %s(%d): ret=%d%s ev=%#x ", cmd, cmdstep, __FUNCTION__, fd, ret, get_errno(ret), ret > 0 ? fds.revents : 0);
+		if (ret > 0 && fds.revents) {
+			int flags, flag;
+			putchar('(');
+
+			for (flags = fds.revents; flags; flags ^= flag) {
+				flag = flags ^ (flags & (flags - 1)); // keep lowest bit only
+				switch (flag) {
+				case POLLIN: printf("IN"); break;
+				case POLLOUT: printf("OUT"); break;
+				case POLLPRI: printf("PRI"); break;
+				case POLLHUP: printf("HUP"); break;
+				case POLLERR: printf("ERR"); break;
+				case POLLNVAL: printf("NVAL"); break;
+#if POLLRDHUP
+				case POLLRDHUP: printf("RDHUP"); break;
+#endif
+				default: printf("???[%#x]", flag); break;
+				}
+				if (flags ^ flag)
+					putchar(' ');
+			}
+			putchar(')');
+		}
+		putchar('\n');
+	}
+}
+
+int main(int argc, char **argv)
+{
+	const char *arg0;
+	char *word, *next;
+	int fd;
+
+	/* listener */
+	lfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (lfd < 0)
+		die("socket(l)");
+
+	setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+
+	memset(&saddr, 0, sizeof(saddr));
+        saddr.sin_family = AF_INET;
+        saddr.sin_port = htons(0);
+	salen = sizeof(saddr);
+
+	if (bind(lfd, (struct sockaddr *)&saddr, salen) < 0)
+		die("bind()");
+
+	if (listen(lfd, 1000) < 0)
+		die("listen()");
+
+	if (getsockname(lfd, (struct sockaddr *)&saddr, &salen) < 0)
+		die("getsockname()");
+
+
+	/* client */
+	cfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (cfd < 0)
+		die("socket(c)");
+
+        if (connect(cfd, (const struct sockaddr*)&saddr, salen) == -1)
+		die("connect()");
+
+	/* connection is pending in accept queue, accept() will either be
+	 * explicit with "-l acc" below, or implicit on "-s <cmd>"
+	 */
+
+	arg0 = argv[0];
+	if (argc < 2) {
+		usage(arg0);
+		exit(1);
+	}
+
+	write(1, "#### BEGIN ####\n", 16); // add a visible delimiter in the traces
+
+	while (argc > 1) {
+		argc--; argv++;
+		if (**argv != '-') {
+			usage(arg0);
+			exit(1);
+		}
+
+		fd = -1;
+		switch (argv[0][1]) {
+		case 'h' :
+			usage(arg0);
+			exit(0);
+			break;
+		case 'v' :
+			verbose++;
+			break;
+		case 'c' :
+			cmd++; cmdstep = 0;
+			fd = cfd;
+			break;
+		case 's' :
+			cmd++; cmdstep = 0;
+			if (sfd < 0)
+				do_acc(lfd);
+			if (sfd < 0)
+				die("accept()");
+			fd = sfd;
+			break;
+		case 'l' :
+			cmd++; cmdstep = 0;
+			fd = lfd;
+			break;
+		default  : usage(arg0); exit(1); break;
+		}
+
+		if (fd >= 0) { /* an action is required */
+			if (argc < 2) {
+				usage(arg0);
+				exit(1);
+			}
+
+			for (word = argv[1]; word && *word; word = next) {
+				next = strchr(word, ',');
+				if (next)
+					*(next++) = 0;
+				cmdstep++;
+				if (strcmp(word, "acc") == 0) {
+					do_acc(fd);
+				}
+				else if (strcmp(word, "snd") == 0) {
+					do_snd(fd);
+				}
+				else if (strcmp(word, "mor") == 0) {
+					do_mor(fd);
+				}
+				else if (strcmp(word, "rcv") == 0) {
+					do_rcv(fd);
+				}
+				else if (strcmp(word, "drn") == 0) {
+					do_drn(fd);
+				}
+				else if (strcmp(word, "shb") == 0) {
+					do_shb(fd);
+				}
+				else if (strcmp(word, "shr") == 0) {
+					do_shr(fd);
+				}
+				else if (strcmp(word, "shw") == 0) {
+					do_shw(fd);
+				}
+				else if (strcmp(word, "lin") == 0) {
+					do_lin(fd);
+				}
+				else if (strcmp(word, "clo") == 0) {
+					do_clo(fd);
+				}
+				else if (strcmp(word, "pol") == 0) {
+					do_pol(fd);
+				}
+				else {
+					printf("Ignoring unknown action '%s' in step #%d of cmd #%d\n", word, cmdstep, cmd);
+				}
+			}
+			argc--; argv++;
+		}
+	}
+
+	write(1, "#### END ####\n", 14); // add a visible delimiter in the traces
+
+	if (!cmd) {
+		printf("No command was requested!\n");
+		usage(arg0);
+		exit(1);
+	}
+
+	return 0;
+}