diff --git a/src/core/client_config/connector.c b/src/core/client_config/connector.c
index a8cd5fc1490..c1e583e4a50 100644
--- a/src/core/client_config/connector.c
+++ b/src/core/client_config/connector.c
@@ -47,3 +47,7 @@ void grpc_connector_connect(grpc_connector *connector,
                             grpc_iomgr_closure *notify) {
   connector->vtable->connect(connector, in_args, out_args, notify);
 }
+
+void grpc_connector_shutdown(grpc_connector *connector) {
+  connector->vtable->shutdown(connector);
+}
diff --git a/src/core/client_config/connector.h b/src/core/client_config/connector.h
index bdaeda86aee..ad0b5675539 100644
--- a/src/core/client_config/connector.h
+++ b/src/core/client_config/connector.h
@@ -72,6 +72,9 @@ typedef struct {
 struct grpc_connector_vtable {
   void (*ref)(grpc_connector *connector);
   void (*unref)(grpc_connector *connector);
+  /** Implementation of grpc_connector_shutdown */
+  void (*shutdown)(grpc_connector *connector);
+  /** Implementation of grpc_connector_connect */
   void (*connect)(grpc_connector *connector,
                   const grpc_connect_in_args *in_args,
                   grpc_connect_out_args *out_args, grpc_iomgr_closure *notify);
@@ -79,9 +82,12 @@ struct grpc_connector_vtable {
 
 void grpc_connector_ref(grpc_connector *connector);
 void grpc_connector_unref(grpc_connector *connector);
+/** Connect using the connector: max one outstanding call at a time */
 void grpc_connector_connect(grpc_connector *connector,
                             const grpc_connect_in_args *in_args,
                             grpc_connect_out_args *out_args,
                             grpc_iomgr_closure *notify);
+/** Cancel any pending connection */
+void grpc_connector_shutdown(grpc_connector *connector);
 
 #endif
diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index 82212d2c6b4..99479b79c51 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -443,6 +443,10 @@ void grpc_subchannel_process_transport_op(grpc_subchannel *c,
   if (cancel_alarm) {
     grpc_alarm_cancel(&c->alarm);
   }
+
+  if (op->disconnect) {
+    grpc_connector_shutdown(c->connector);
+  }
 }
 
 static void on_state_changed(void *p, int iomgr_success) {
diff --git a/src/core/client_config/subchannel.h b/src/core/client_config/subchannel.h
index 2e36c69134a..29a0b67d2da 100644
--- a/src/core/client_config/subchannel.h
+++ b/src/core/client_config/subchannel.h
@@ -43,6 +43,7 @@ typedef struct grpc_subchannel grpc_subchannel;
 typedef struct grpc_subchannel_call grpc_subchannel_call;
 typedef struct grpc_subchannel_args grpc_subchannel_args;
 
+#define GRPC_SUBCHANNEL_REFCOUNT_DEBUG
 #ifdef GRPC_SUBCHANNEL_REFCOUNT_DEBUG
 #define GRPC_SUBCHANNEL_REF(p, r) \
   grpc_subchannel_ref((p), __FILE__, __LINE__, (r))
diff --git a/src/core/iomgr/fd_posix.c b/src/core/iomgr/fd_posix.c
index 4bca9f3f6e3..69518597d57 100644
--- a/src/core/iomgr/fd_posix.c
+++ b/src/core/iomgr/fd_posix.c
@@ -222,10 +222,9 @@ void grpc_fd_orphan(grpc_fd *fd, grpc_iomgr_closure *on_done,
                     const char *reason) {
   fd->on_done_closure = on_done;
   shutdown(fd->fd, SHUT_RDWR);
-  REF_BY(fd, 1, reason); /* remove active status, but keep referenced */
   gpr_mu_lock(&fd->watcher_mu);
+  REF_BY(fd, 1, reason); /* remove active status, but keep referenced */
   if (!has_watchers(fd)) {
-    GPR_ASSERT(!fd->closed);
     fd->closed = 1;
     close(fd->fd);
     if (fd->on_done_closure) {
diff --git a/src/core/iomgr/iomgr.c b/src/core/iomgr/iomgr.c
index 66d7e9b1103..5d1fc687673 100644
--- a/src/core/iomgr/iomgr.c
+++ b/src/core/iomgr/iomgr.c
@@ -34,16 +34,18 @@
 #include "src/core/iomgr/iomgr.h"
 
 #include <stdlib.h>
+#include <string.h>
 
-#include "src/core/iomgr/iomgr_internal.h"
-#include "src/core/iomgr/alarm_internal.h"
-#include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/sync.h>
 #include <grpc/support/thd.h>
 
+#include "src/core/iomgr/iomgr_internal.h"
+#include "src/core/iomgr/alarm_internal.h"
+#include "src/core/support/string.h"
+
 static gpr_mu g_mu;
 static gpr_cv g_rcv;
 static int g_shutdown;
@@ -124,6 +126,8 @@ void grpc_iomgr_shutdown(void) {
   }
   gpr_mu_unlock(&g_mu);
 
+  memset(&g_root_object, 0, sizeof(g_root_object));
+
   grpc_alarm_list_shutdown();
 
   grpc_iomgr_platform_shutdown();
diff --git a/src/core/iomgr/pollset_multipoller_with_epoll.c b/src/core/iomgr/pollset_multipoller_with_epoll.c
index 971b7b4a01e..12f34c1a195 100644
--- a/src/core/iomgr/pollset_multipoller_with_epoll.c
+++ b/src/core/iomgr/pollset_multipoller_with_epoll.c
@@ -72,7 +72,7 @@ static void finally_add_fd(grpc_pollset *pollset, grpc_fd *fd) {
      to this pollset whilst adding, but that should be benign. */
   GPR_ASSERT(grpc_fd_begin_poll(fd, pollset, 0, 0, &watcher) == 0);
   if (watcher.fd != NULL) {
-    ev.events = EPOLLIN | EPOLLOUT | EPOLLET;
+    ev.events = (uint32_t)(EPOLLIN | EPOLLOUT | EPOLLET);
     ev.data.ptr = fd;
     err = epoll_ctl(h->epoll_fd, EPOLL_CTL_ADD, fd->fd, &ev);
     if (err < 0) {
diff --git a/src/core/iomgr/udp_server.c b/src/core/iomgr/udp_server.c
index d4e8e99bce1..96688054fbf 100644
--- a/src/core/iomgr/udp_server.c
+++ b/src/core/iomgr/udp_server.c
@@ -94,9 +94,6 @@ static void unlink_if_unix_domain_socket(const struct sockaddr_un *un) {
 
 /* the overall server */
 struct grpc_udp_server {
-  grpc_udp_server_cb cb;
-  void *cb_arg;
-
   gpr_mu mu;
   gpr_cv cv;
 
@@ -132,8 +129,6 @@ grpc_udp_server *grpc_udp_server_create(void) {
   s->active_ports = 0;
   s->destroyed_ports = 0;
   s->shutdown = 0;
-  s->cb = NULL;
-  s->cb_arg = NULL;
   s->ports = gpr_malloc(sizeof(server_port) * INIT_PORT_CAP);
   s->nports = 0;
   s->port_capacity = INIT_PORT_CAP;
@@ -236,6 +231,11 @@ static int prepare_socket(int fd, const struct sockaddr *addr,
     goto error;
   }
 
+  if (!grpc_set_socket_nonblocking(fd, 1) || !grpc_set_socket_cloexec(fd, 1)) {
+    gpr_log(GPR_ERROR, "Unable to configure socket %d: %s", fd,
+            strerror(errno));
+  }
+
   get_local_ip = 1;
   rc = setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &get_local_ip,
                   sizeof(get_local_ip));
@@ -286,7 +286,7 @@ static void on_read(void *arg, int success) {
 
   /* Tell the registered callback that data is available to read. */
   GPR_ASSERT(sp->read_cb);
-  sp->read_cb(sp->fd, sp->server->cb, sp->server->cb_arg);
+  sp->read_cb(sp->fd);
 
   /* Re-arm the notification event so we get another chance to read. */
   grpc_fd_notify_on_read(sp->emfd, &sp->read_closure);
@@ -305,7 +305,6 @@ static int add_socket_to_server(grpc_udp_server *s, int fd,
     grpc_sockaddr_to_string(&addr_str, (struct sockaddr *)&addr, 1);
     gpr_asprintf(&name, "udp-server-listener:%s", addr_str);
     gpr_mu_lock(&s->mu);
-    GPR_ASSERT(!s->cb && "must add ports before starting server");
     /* append it to the list under a lock */
     if (s->nports == s->port_capacity) {
       s->port_capacity *= 2;
@@ -411,15 +410,10 @@ int grpc_udp_server_get_fd(grpc_udp_server *s, unsigned index) {
 }
 
 void grpc_udp_server_start(grpc_udp_server *s, grpc_pollset **pollsets,
-                           size_t pollset_count,
-                           grpc_udp_server_cb new_transport_cb, void *cb_arg) {
+                           size_t pollset_count) {
   size_t i, j;
-  GPR_ASSERT(new_transport_cb);
   gpr_mu_lock(&s->mu);
-  GPR_ASSERT(!s->cb);
   GPR_ASSERT(s->active_ports == 0);
-  s->cb = new_transport_cb;
-  s->cb_arg = cb_arg;
   s->pollsets = pollsets;
   for (i = 0; i < s->nports; i++) {
     for (j = 0; j < pollset_count; j++) {
diff --git a/src/core/iomgr/udp_server.h b/src/core/iomgr/udp_server.h
index 389f84eccad..c930e81cbc6 100644
--- a/src/core/iomgr/udp_server.h
+++ b/src/core/iomgr/udp_server.h
@@ -39,21 +39,15 @@
 /* Forward decl of grpc_udp_server */
 typedef struct grpc_udp_server grpc_udp_server;
 
-/* New server callback: ep is the newly connected connection */
-typedef void (*grpc_udp_server_cb)(void *arg, grpc_endpoint *ep);
-
 /* Called when data is available to read from the socket. */
-typedef void (*grpc_udp_server_read_cb)(int fd,
-                                        grpc_udp_server_cb new_transport_cb,
-                                        void *cb_arg);
+typedef void (*grpc_udp_server_read_cb)(int fd);
 
 /* Create a server, initially not bound to any ports */
 grpc_udp_server *grpc_udp_server_create(void);
 
 /* Start listening to bound ports */
-void grpc_udp_server_start(grpc_udp_server *server, grpc_pollset **pollsets,
-                           size_t pollset_count, grpc_udp_server_cb cb,
-                           void *cb_arg);
+void grpc_udp_server_start(grpc_udp_server *udp_server, grpc_pollset **pollsets,
+                           size_t pollset_count);
 
 int grpc_udp_server_get_fd(grpc_udp_server *s, unsigned index);
 
diff --git a/src/core/support/string.c b/src/core/support/string.c
index af0389ea832..e0ffeb8a4af 100644
--- a/src/core/support/string.c
+++ b/src/core/support/string.c
@@ -101,7 +101,7 @@ static void asciidump(dump_out *out, const char *buf, size_t len) {
     dump_out_append(out, '\'');
   }
   for (cur = beg; cur != end; ++cur) {
-    dump_out_append(out, isprint(*cur) ? *(char *)cur : '.');
+    dump_out_append(out, (char)(isprint(*cur) ? *(char *)cur : '.'));
   }
   if (!out_was_empty) {
     dump_out_append(out, '\'');
diff --git a/src/core/surface/channel_create.c b/src/core/surface/channel_create.c
index 7a4ec00abb7..908c07b752e 100644
--- a/src/core/surface/channel_create.c
+++ b/src/core/surface/channel_create.c
@@ -89,6 +89,8 @@ static void connected(void *arg, grpc_endpoint *tcp) {
   notify->cb(notify->cb_arg, 1);
 }
 
+static void connector_shutdown(grpc_connector *con) {}
+
 static void connector_connect(grpc_connector *con,
                               const grpc_connect_in_args *args,
                               grpc_connect_out_args *result,
@@ -105,7 +107,7 @@ static void connector_connect(grpc_connector *con,
 }
 
 static const grpc_connector_vtable connector_vtable = {
-    connector_ref, connector_unref, connector_connect};
+    connector_ref, connector_unref, connector_shutdown, connector_connect};
 
 typedef struct {
   grpc_subchannel_factory base;
diff --git a/src/core/surface/secure_channel_create.c b/src/core/surface/secure_channel_create.c
index ec077af8dd2..690612d1647 100644
--- a/src/core/surface/secure_channel_create.c
+++ b/src/core/surface/secure_channel_create.c
@@ -61,6 +61,9 @@ typedef struct {
   grpc_iomgr_closure *notify;
   grpc_connect_in_args args;
   grpc_connect_out_args *result;
+
+  gpr_mu mu;
+  grpc_endpoint *connecting_endpoint;
 } connector;
 
 static void connector_ref(grpc_connector *con) {
@@ -81,10 +84,20 @@ static void on_secure_transport_setup_done(void *arg,
                                            grpc_endpoint *secure_endpoint) {
   connector *c = arg;
   grpc_iomgr_closure *notify;
-  if (status != GRPC_SECURITY_OK) {
+  gpr_mu_lock(&c->mu);
+  if (c->connecting_endpoint == NULL) {
+    memset(c->result, 0, sizeof(*c->result));
+    gpr_mu_unlock(&c->mu);
+  } else if (status != GRPC_SECURITY_OK) {
+    GPR_ASSERT(c->connecting_endpoint == wrapped_endpoint);
     gpr_log(GPR_ERROR, "Secure transport setup failed with error %d.", status);
     memset(c->result, 0, sizeof(*c->result));
+    c->connecting_endpoint = NULL;
+    gpr_mu_unlock(&c->mu);
   } else {
+    GPR_ASSERT(c->connecting_endpoint == wrapped_endpoint);
+    c->connecting_endpoint = NULL;
+    gpr_mu_unlock(&c->mu);
     c->result->transport = grpc_create_chttp2_transport(
         c->args.channel_args, secure_endpoint, c->args.metadata_context,
         c->args.workqueue, 1);
@@ -103,6 +116,10 @@ static void connected(void *arg, grpc_endpoint *tcp) {
   connector *c = arg;
   grpc_iomgr_closure *notify;
   if (tcp != NULL) {
+    gpr_mu_lock(&c->mu);
+    GPR_ASSERT(c->connecting_endpoint == NULL);
+    c->connecting_endpoint = tcp;
+    gpr_mu_unlock(&c->mu);
     grpc_setup_secure_transport(&c->security_connector->base, tcp,
                                 on_secure_transport_setup_done, c);
   } else {
@@ -113,6 +130,18 @@ static void connected(void *arg, grpc_endpoint *tcp) {
   }
 }
 
+static void connector_shutdown(grpc_connector *con) {
+  connector *c = (connector *)con;
+  grpc_endpoint *ep;
+  gpr_mu_lock(&c->mu);
+  ep = c->connecting_endpoint;
+  c->connecting_endpoint = NULL;
+  gpr_mu_unlock(&c->mu);
+  if (ep) {
+    grpc_endpoint_shutdown(ep);
+  }
+}
+
 static void connector_connect(grpc_connector *con,
                               const grpc_connect_in_args *args,
                               grpc_connect_out_args *result,
@@ -123,13 +152,16 @@ static void connector_connect(grpc_connector *con,
   c->notify = notify;
   c->args = *args;
   c->result = result;
+  gpr_mu_lock(&c->mu);
+  GPR_ASSERT(c->connecting_endpoint == NULL);
+  gpr_mu_unlock(&c->mu);
   grpc_tcp_client_connect(connected, c, args->interested_parties,
                           args->workqueue, args->addr, args->addr_len,
                           args->deadline);
 }
 
 static const grpc_connector_vtable connector_vtable = {
-    connector_ref, connector_unref, connector_connect};
+    connector_ref, connector_unref, connector_shutdown, connector_connect};
 
 typedef struct {
   grpc_subchannel_factory base;
diff --git a/src/core/transport/chttp2/parsing.c b/src/core/transport/chttp2/parsing.c
index a592ce7d28b..f26f4467872 100644
--- a/src/core/transport/chttp2/parsing.c
+++ b/src/core/transport/chttp2/parsing.c
@@ -486,7 +486,7 @@ static int init_skip_frame_parser(
     transport_parsing->hpack_parser.on_header_user_data = NULL;
     transport_parsing->hpack_parser.is_boundary = is_eoh;
     transport_parsing->hpack_parser.is_eof =
-        is_eoh ? transport_parsing->header_eof : 0;
+        (gpr_uint8)(is_eoh ? transport_parsing->header_eof : 0);
   } else {
     transport_parsing->parser = skip_parser;
   }
@@ -696,7 +696,7 @@ static int init_header_frame_parser(
   transport_parsing->hpack_parser.on_header_user_data = transport_parsing;
   transport_parsing->hpack_parser.is_boundary = is_eoh;
   transport_parsing->hpack_parser.is_eof =
-      is_eoh ? transport_parsing->header_eof : 0;
+      (gpr_uint8)(is_eoh ? transport_parsing->header_eof : 0);
   if (!is_continuation && (transport_parsing->incoming_frame_flags &
                            GRPC_CHTTP2_FLAG_HAS_PRIORITY)) {
     grpc_chttp2_hpack_parser_set_has_priority(&transport_parsing->hpack_parser);
diff --git a/test/core/iomgr/udp_server_test.c b/test/core/iomgr/udp_server_test.c
index c4f1896ba6a..24b6b1c717b 100644
--- a/test/core/iomgr/udp_server_test.c
+++ b/test/core/iomgr/udp_server_test.c
@@ -49,9 +49,7 @@ static grpc_pollset g_pollset;
 static int g_number_of_reads = 0;
 static int g_number_of_bytes_read = 0;
 
-static void on_connect(void *arg, grpc_endpoint *udp) {}
-
-static void on_read(int fd, grpc_udp_server_cb new_transport_cb, void *cb_arg) {
+static void on_read(int fd) {
   char read_buffer[512];
   ssize_t byte_count;
 
@@ -73,7 +71,7 @@ static void test_no_op(void) {
 static void test_no_op_with_start(void) {
   grpc_udp_server *s = grpc_udp_server_create();
   LOG_TEST("test_no_op_with_start");
-  grpc_udp_server_start(s, NULL, 0, on_connect, NULL);
+  grpc_udp_server_start(s, NULL, 0);
   grpc_udp_server_destroy(s, NULL, NULL);
 }
 
@@ -100,7 +98,7 @@ static void test_no_op_with_port_and_start(void) {
   GPR_ASSERT(grpc_udp_server_add_port(s, (struct sockaddr *)&addr, sizeof(addr),
                                       on_read));
 
-  grpc_udp_server_start(s, NULL, 0, on_connect, NULL);
+  grpc_udp_server_start(s, NULL, 0);
 
   grpc_udp_server_destroy(s, NULL, NULL);
 }
@@ -130,7 +128,7 @@ static void test_receive(int number_of_clients) {
   GPR_ASSERT(addr_len <= sizeof(addr));
 
   pollsets[0] = &g_pollset;
-  grpc_udp_server_start(s, pollsets, 1, on_connect, NULL);
+  grpc_udp_server_start(s, pollsets, 1);
 
   gpr_mu_lock(GRPC_POLLSET_MU(&g_pollset));
 
diff --git a/test/core/util/port_posix.c b/test/core/util/port_posix.c
index be45bae4960..03f4c4912e9 100644
--- a/test/core/util/port_posix.c
+++ b/test/core/util/port_posix.c
@@ -47,6 +47,7 @@
 #include <grpc/grpc.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
 
 #include "src/core/httpcli/httpcli.h"
 #include "src/core/support/env.h"
@@ -66,7 +67,70 @@ static int has_port_been_chosen(int port) {
   return 0;
 }
 
-static void free_chosen_ports() { gpr_free(chosen_ports); }
+typedef struct freereq {
+  grpc_pollset pollset;
+  int done;
+} freereq;
+
+static void destroy_pollset_and_shutdown(void *p) {
+  grpc_pollset_destroy(p);
+  grpc_shutdown();
+}
+
+static void freed_port_from_server(void *arg,
+                                   const grpc_httpcli_response *response) {
+  freereq *pr = arg;
+  gpr_mu_lock(GRPC_POLLSET_MU(&pr->pollset));
+  pr->done = 1;
+  grpc_pollset_kick(&pr->pollset, NULL);
+  gpr_mu_unlock(GRPC_POLLSET_MU(&pr->pollset));
+}
+
+static void free_port_using_server(char *server, int port) {
+  grpc_httpcli_context context;
+  grpc_httpcli_request req;
+  freereq pr;
+  char *path;
+
+  grpc_init();
+
+  memset(&pr, 0, sizeof(pr));
+  memset(&req, 0, sizeof(req));
+  grpc_pollset_init(&pr.pollset);
+
+  req.host = server;
+  gpr_asprintf(&path, "/drop/%d", port);
+  req.path = path;
+
+  grpc_httpcli_context_init(&context);
+  grpc_httpcli_get(&context, &pr.pollset, &req,
+                   GRPC_TIMEOUT_SECONDS_TO_DEADLINE(10), freed_port_from_server,
+                   &pr);
+  gpr_mu_lock(GRPC_POLLSET_MU(&pr.pollset));
+  while (!pr.done) {
+    grpc_pollset_worker worker;
+    grpc_pollset_work(&pr.pollset, &worker, gpr_now(GPR_CLOCK_MONOTONIC),
+                      GRPC_TIMEOUT_SECONDS_TO_DEADLINE(1));
+  }
+  gpr_mu_unlock(GRPC_POLLSET_MU(&pr.pollset));
+
+  grpc_httpcli_context_destroy(&context);
+  grpc_pollset_shutdown(&pr.pollset, destroy_pollset_and_shutdown, &pr.pollset);
+  gpr_free(path);
+}
+
+static void free_chosen_ports() { 
+  char *env = gpr_getenv("GRPC_TEST_PORT_SERVER");
+  if (env != NULL) {
+    size_t i;
+    for (i = 0; i < num_chosen_ports; i++) {
+      free_port_using_server(env, chosen_ports[i]);
+    }
+    gpr_free(env);
+  }
+
+  gpr_free(chosen_ports); 
+}
 
 static void chose_port(int port) {
   if (chosen_ports == NULL) {
@@ -131,6 +195,9 @@ static int is_port_available(int *port, int is_tcp) {
 typedef struct portreq {
   grpc_pollset pollset;
   int port;
+  int retries;
+  char *server;
+  grpc_httpcli_context *ctx;
 } portreq;
 
 static void got_port_from_server(void *arg,
@@ -138,6 +205,19 @@ static void got_port_from_server(void *arg,
   size_t i;
   int port = 0;
   portreq *pr = arg;
+  if (!response || response->status != 200) {
+    grpc_httpcli_request req;
+    memset(&req, 0, sizeof(req));
+    GPR_ASSERT(pr->retries < 10);
+    pr->retries++;
+    req.host = pr->server;
+    req.path = "/get";
+    gpr_log(GPR_DEBUG, "failed port pick from server: retrying");
+    sleep(1);
+    grpc_httpcli_get(pr->ctx, &pr->pollset, &req, GRPC_TIMEOUT_SECONDS_TO_DEADLINE(10), 
+                     got_port_from_server, pr);
+    return;
+  }
   GPR_ASSERT(response);
   GPR_ASSERT(response->status == 200);
   for (i = 0; i < response->body_length; i++) {
@@ -151,11 +231,6 @@ static void got_port_from_server(void *arg,
   gpr_mu_unlock(GRPC_POLLSET_MU(&pr->pollset));
 }
 
-static void destroy_pollset_and_shutdown(void *p) {
-  grpc_pollset_destroy(p);
-  grpc_shutdown();
-}
-
 static int pick_port_using_server(char *server) {
   grpc_httpcli_context context;
   grpc_httpcli_request req;
@@ -167,6 +242,8 @@ static int pick_port_using_server(char *server) {
   memset(&req, 0, sizeof(req));
   grpc_pollset_init(&pr.pollset);
   pr.port = -1;
+  pr.server = server;
+  pr.ctx = &context;
 
   req.host = server;
   req.path = "/get";
@@ -211,8 +288,9 @@ int grpc_pick_unused_port(void) {
     int port = pick_port_using_server(env);
     gpr_free(env);
     if (port != 0) {
-      return port;
+      chose_port(port);
     }
+    return port;
   }
 
   for (;;) {
diff --git a/tools/jenkins/run_jenkins.sh b/tools/jenkins/run_jenkins.sh
index 0f15835ea88..9ff588e8fa4 100755
--- a/tools/jenkins/run_jenkins.sh
+++ b/tools/jenkins/run_jenkins.sh
@@ -79,7 +79,6 @@ then
     -e "config=$config" \
     -e "language=$language" \
     -e "arch=$arch" \
-    -e "GRPC_ZOOKEEPER_SERVER_TEST=grpc-jenkins-master:2181" \
     -e CCACHE_DIR=/tmp/ccache \
     -i \
     -v "$git_root:/var/local/jenkins/grpc" \
diff --git a/tools/run_tests/port_server.py b/tools/run_tests/port_server.py
index 0f81470d28f..d14c829fe06 100755
--- a/tools/run_tests/port_server.py
+++ b/tools/run_tests/port_server.py
@@ -37,6 +37,7 @@ import os
 import socket
 import sys
 import time
+import yaml
 
 argp = argparse.ArgumentParser(description='Server for httpcli_test')
 argp.add_argument('-p', '--port', default=12345, type=int)
@@ -51,16 +52,17 @@ with open(__file__) as f:
   _MY_VERSION = hashlib.sha1(f.read()).hexdigest()
 
 
-def refill_pool():
+def refill_pool(max_timeout):
   """Scan for ports not marked for being in use"""
-  for i in range(10000, 65000):
+  for i in range(1025, 32767):
     if len(pool) > 100: break
     if i in in_use:
       age = time.time() - in_use[i]
-      if age < 600:
+      if age < max_timeout:
         continue
       del in_use[i]
     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
     try:
       s.bind(('localhost', i))
       pool.append(i)
@@ -73,8 +75,12 @@ def refill_pool():
 def allocate_port():
   global pool
   global in_use
-  if not pool:
-    refill_pool()
+  max_timeout = 600
+  while not pool:
+    refill_pool(max_timeout)
+    if not pool:
+      time.sleep(1)
+      max_timeout /= 2
   port = pool[0]
   pool = pool[1:]
   in_use[port] = time.time()
@@ -97,12 +103,26 @@ class Handler(BaseHTTPServer.BaseHTTPRequestHandler):
       p = allocate_port()
       self.log_message('allocated port %d' % p)
       self.wfile.write('%d' % p)
+    elif self.path[0:6] == '/drop/':
+      self.send_response(200)
+      self.send_header('Content-Type', 'text/plain')
+      self.end_headers()
+      p = int(self.path[6:])
+      del in_use[p]
+      pool.append(p)
+      self.log_message('drop port %d' % p)
     elif self.path == '/version':
       # fetch a version string and the current process pid
       self.send_response(200)
       self.send_header('Content-Type', 'text/plain')
       self.end_headers()
       self.wfile.write(_MY_VERSION)
+    elif self.path == '/dump':
+      self.send_response(200)
+      self.send_header('Content-Type', 'text/plain')
+      self.end_headers()
+      now = time.time()
+      self.wfile.write(yaml.dump({'pool': pool, 'in_use': dict((k, now - v) for k, v in in_use.iteritems())}))
     elif self.path == '/quit':
       self.send_response(200)
       self.end_headers()