Merge pull request #14610 from apolcyn/python_dig

 Remove the C++ test dependency on dig and dnsutils

bazel/grpc_build_system.bzl

@@ -174,6 +174,7 @@ def grpc_py_binary(name, srcs, data = [], deps = [], external_deps = [], testonl
   native.py_binary(
     name = name,
     srcs = srcs,
+    testonly = testonly,
     data = data,
     deps = deps + _get_external_deps(external_deps)
   )

templates/test/cpp/naming/resolver_component_tests_defs.include

@@ -21,9 +21,11 @@ set -ex
 FLAGS_test_bin_path=$(echo "$1" | grep '\--test_bin_path=' | cut -d "=" -f 2)
 FLAGS_dns_server_bin_path=$(echo "$2" | grep '\--dns_server_bin_path=' | cut -d "=" -f 2)
 FLAGS_records_config_path=$(echo "$3" | grep '\--records_config_path=' | cut -d "=" -f 2)
-FLAGS_test_dns_server_port=$(echo "$4" | grep '\--test_dns_server_port=' | cut -d "=" -f 2)
+FLAGS_dns_server_port=$(echo "$4" | grep '\--dns_server_port=' | cut -d "=" -f 2)
+FLAGS_dns_resolver_bin_path=$(echo "$5" | grep '\--dns_resolver_bin_path=' | cut -d "=" -f 2)
+FLAGS_tcp_connect_bin_path=$(echo "$6" | grep '\--tcp_connect_bin_path=' | cut -d "=" -f 2)
 
-for cmd_arg in "$FLAGS_test_bin_path" "$FLAGS_dns_server_bin_path" "$FLAGS_records_config_path" "$FLAGS_test_dns_server_port"; do
+for cmd_arg in "$FLAGS_test_bin_path" "$FLAGS_dns_server_bin_path" "$FLAGS_records_config_path" "$FLAGS_dns_server_port" "$FLAGS_dns_resolver_bin_path" "$FLAGS_tcp_connect_bin_path"; do
   if [[ "$cmd_arg" == "" ]]; then
     echo "Missing a CMD arg" && exit 1
   fi
@@ -34,17 +36,17 @@ if [[ "$GRPC_DNS_RESOLVER" != "" && "$GRPC_DNS_RESOLVER" != ares ]]; then
 fi
 export GRPC_DNS_RESOLVER=ares
 
-"$FLAGS_dns_server_bin_path" --records_config_path="$FLAGS_records_config_path" --port="$FLAGS_test_dns_server_port" > /dev/null 2>&1 &
+"$FLAGS_dns_server_bin_path" --records_config_path="$FLAGS_records_config_path" --port="$FLAGS_dns_server_port" > /dev/null 2>&1 &
 DNS_SERVER_PID=$!
 echo "Local DNS server started. PID: $DNS_SERVER_PID"
 
 # Health check local DNS server TCP and UDP ports
 for ((i=0;i<30;i++));
 do
-  echo "Retry health-check DNS query to local DNS server over tcp and udp"
+  echo "Retry health-check local DNS server by attempting a DNS query and TCP handshake"
   RETRY=0
-  dig A health-check-local-dns-server-is-alive.resolver-tests.grpctestingexp. @localhost -p "$FLAGS_test_dns_server_port" +tries=1 +timeout=1 | grep '123.123.123.123' || RETRY=1
-  dig A health-check-local-dns-server-is-alive.resolver-tests.grpctestingexp. @localhost -p "$FLAGS_test_dns_server_port" +tries=1 +timeout=1 +tcp | grep '123.123.123.123' || RETRY=1
+  $FLAGS_dns_resolver_bin_path -s 127.0.0.1 -p "$FLAGS_dns_server_port" -n health-check-local-dns-server-is-alive.resolver-tests.grpctestingexp. -t 1 | grep '123.123.123.123' || RETRY=1
+  $FLAGS_tcp_connect_bin_path -s 127.0.0.1 -p "$FLAGS_dns_server_port" -t 1 || RETRY=1
   if [[ "$RETRY" == 0 ]]; then
     break
   fi;
@@ -83,7 +85,7 @@ $FLAGS_test_bin_path \\
 
   --expected_lb_policy='${test['expected_lb_policy']}' \\
 
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 % endfor

test/cpp/naming/BUILD

@@ -34,17 +34,4 @@ grpc_sh_binary(
     ],
 )
 
-grpc_py_binary(
-  name = "test_dns_server",
-  srcs = ["test_dns_server.py"],
-  testonly = True,
-  data = [
-      "resolver_test_record_groups.yaml",
-  ],
-  external_deps = [
-      "twisted",
-      "yaml",
-  ]
-)
-
 generate_resolver_component_tests()

test/cpp/naming/generate_resolver_component_tests.bzl

@@ -54,7 +54,9 @@ def generate_resolver_component_tests():
         data = [
             ":resolver_component_tests_runner",
             ":resolver_component_test%s" % unsecure_build_config_suffix,
-            ":test_dns_server",
+            "//test/cpp/naming/utils:dns_server",
+            "//test/cpp/naming/utils:dns_resolver",
+            "//test/cpp/naming/utils:tcp_connect",
             "resolver_test_record_groups.yaml", # include the transitive dependency so that the dns sever py binary can locate this
         ],
         args = [

test/cpp/naming/resolver_component_tests_runner.sh

@@ -21,9 +21,11 @@ set -ex
 FLAGS_test_bin_path=$(echo "$1" | grep '\--test_bin_path=' | cut -d "=" -f 2)
 FLAGS_dns_server_bin_path=$(echo "$2" | grep '\--dns_server_bin_path=' | cut -d "=" -f 2)
 FLAGS_records_config_path=$(echo "$3" | grep '\--records_config_path=' | cut -d "=" -f 2)
-FLAGS_test_dns_server_port=$(echo "$4" | grep '\--test_dns_server_port=' | cut -d "=" -f 2)
+FLAGS_dns_server_port=$(echo "$4" | grep '\--dns_server_port=' | cut -d "=" -f 2)
+FLAGS_dns_resolver_bin_path=$(echo "$5" | grep '\--dns_resolver_bin_path=' | cut -d "=" -f 2)
+FLAGS_tcp_connect_bin_path=$(echo "$6" | grep '\--tcp_connect_bin_path=' | cut -d "=" -f 2)
 
-for cmd_arg in "$FLAGS_test_bin_path" "$FLAGS_dns_server_bin_path" "$FLAGS_records_config_path" "$FLAGS_test_dns_server_port"; do
+for cmd_arg in "$FLAGS_test_bin_path" "$FLAGS_dns_server_bin_path" "$FLAGS_records_config_path" "$FLAGS_dns_server_port" "$FLAGS_dns_resolver_bin_path" "$FLAGS_tcp_connect_bin_path"; do
   if [[ "$cmd_arg" == "" ]]; then
     echo "Missing a CMD arg" && exit 1
   fi
@@ -34,17 +36,17 @@ if [[ "$GRPC_DNS_RESOLVER" != "" && "$GRPC_DNS_RESOLVER" != ares ]]; then
 fi
 export GRPC_DNS_RESOLVER=ares
 
-"$FLAGS_dns_server_bin_path" --records_config_path="$FLAGS_records_config_path" --port="$FLAGS_test_dns_server_port" > /dev/null 2>&1 &
+"$FLAGS_dns_server_bin_path" --records_config_path="$FLAGS_records_config_path" --port="$FLAGS_dns_server_port" > /dev/null 2>&1 &
 DNS_SERVER_PID=$!
 echo "Local DNS server started. PID: $DNS_SERVER_PID"
 
 # Health check local DNS server TCP and UDP ports
 for ((i=0;i<30;i++));
 do
-  echo "Retry health-check DNS query to local DNS server over tcp and udp"
+  echo "Retry health-check local DNS server by attempting a DNS query and TCP handshake"
   RETRY=0
-  dig A health-check-local-dns-server-is-alive.resolver-tests.grpctestingexp. @localhost -p "$FLAGS_test_dns_server_port" +tries=1 +timeout=1 | grep '123.123.123.123' || RETRY=1
-  dig A health-check-local-dns-server-is-alive.resolver-tests.grpctestingexp. @localhost -p "$FLAGS_test_dns_server_port" +tries=1 +timeout=1 +tcp | grep '123.123.123.123' || RETRY=1
+  $FLAGS_dns_resolver_bin_path -s 127.0.0.1 -p "$FLAGS_dns_server_port" -n health-check-local-dns-server-is-alive.resolver-tests.grpctestingexp. -t 1 | grep '123.123.123.123' || RETRY=1
+  $FLAGS_tcp_connect_bin_path -s 127.0.0.1 -p "$FLAGS_dns_server_port" -t 1 || RETRY=1
   if [[ "$RETRY" == 0 ]]; then
     break
   fi;
@@ -77,7 +79,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:1234,True' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -85,7 +87,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.5:1234,True;1.2.3.6:1234,True;1.2.3.7:1234,True' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -93,7 +95,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='[2607:f8b0:400a:801::1001]:1234,True' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -101,7 +103,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='[2607:f8b0:400a:801::1002]:1234,True;[2607:f8b0:400a:801::1003]:1234,True;[2607:f8b0:400a:801::1004]:1234,True' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -109,7 +111,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:1234,True' \
   --expected_chosen_service_config='{"loadBalancingPolicy":"round_robin","methodConfig":[{"name":[{"method":"Foo","service":"SimpleService","waitForReady":true}]}]}' \
   --expected_lb_policy='round_robin' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -117,7 +119,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:443,False' \
   --expected_chosen_service_config='{"loadBalancingPolicy":"round_robin","methodConfig":[{"name":[{"method":"Foo","service":"NoSrvSimpleService","waitForReady":true}]}]}' \
   --expected_lb_policy='round_robin' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -125,7 +127,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:443,False' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -133,7 +135,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:443,False' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -141,7 +143,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:443,False' \
   --expected_chosen_service_config='{"loadBalancingPolicy":"round_robin","methodConfig":[{"name":[{"method":"Foo","service":"CppService","waitForReady":true}]}]}' \
   --expected_lb_policy='round_robin' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -149,7 +151,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:443,False' \
   --expected_chosen_service_config='{"loadBalancingPolicy":"round_robin","methodConfig":[{"name":[{"method":"Foo","service":"AlwaysPickedService","waitForReady":true}]}]}' \
   --expected_lb_policy='round_robin' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -157,7 +159,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:1234,True;1.2.3.4:443,False' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -165,7 +167,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='[2607:f8b0:400a:801::1002]:1234,True;[2607:f8b0:400a:801::1002]:443,False' \
   --expected_chosen_service_config='' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 $FLAGS_test_bin_path \
@@ -173,7 +175,7 @@ $FLAGS_test_bin_path \
   --expected_addrs='1.2.3.4:443,False' \
   --expected_chosen_service_config='{"loadBalancingPolicy":"round_robin","methodConfig":[{"name":[{"method":"Foo","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooTwo","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooThree","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooFour","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooFive","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooSix","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooSeven","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooEight","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooNine","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooTen","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooEleven","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooTwelve","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooTwelve","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooTwelve","service":"SimpleService","waitForReady":true}]},{"name":[{"method":"FooTwelve","service":"SimpleService","waitForReady":true}]}]}' \
   --expected_lb_policy='' \
-  --local_dns_server_address="127.0.0.1:$FLAGS_test_dns_server_port" &
+  --local_dns_server_address="127.0.0.1:$FLAGS_dns_server_port" &
 wait "$!" || EXIT_CODE=1
 
 kill -SIGTERM "$DNS_SERVER_PID" || true

test/cpp/naming/resolver_component_tests_runner_invoker.cc

@@ -102,14 +102,18 @@ namespace testing {
 void InvokeResolverComponentTestsRunner(std::string test_runner_bin_path,
                                         std::string test_bin_path,
                                         std::string dns_server_bin_path,
-                                        std::string records_config_path) {
-  int test_dns_server_port = grpc_pick_unused_port_or_die();
-
-  SubProcess* test_driver = new SubProcess(
-      {test_runner_bin_path, "--test_bin_path=" + test_bin_path,
-       "--dns_server_bin_path=" + dns_server_bin_path,
-       "--records_config_path=" + records_config_path,
-       "--test_dns_server_port=" + std::to_string(test_dns_server_port)});
+                                        std::string records_config_path,
+                                        std::string dns_resolver_bin_path,
+                                        std::string tcp_connect_bin_path) {
+  int dns_server_port = grpc_pick_unused_port_or_die();
+
+  SubProcess* test_driver =
+      new SubProcess({test_runner_bin_path, "--test_bin_path=" + test_bin_path,
+                      "--dns_server_bin_path=" + dns_server_bin_path,
+                      "--records_config_path=" + records_config_path,
+                      "--dns_server_port=" + std::to_string(dns_server_port),
+                      "--dns_resolver_bin_path=" + dns_resolver_bin_path,
+                      "--tcp_connect_bin_path=" + tcp_connect_bin_path});
   gpr_mu test_driver_mu;
   gpr_mu_init(&test_driver_mu);
   gpr_cv test_driver_cv;
@@ -170,8 +174,9 @@ int main(int argc, char** argv) {
     // sure that we're using bazel's test environment.
     grpc::testing::InvokeResolverComponentTestsRunner(
         bin_dir + "/resolver_component_tests_runner",
-        bin_dir + "/" + FLAGS_test_bin_name, bin_dir + "/test_dns_server",
-        bin_dir + "/resolver_test_record_groups.yaml");
+        bin_dir + "/" + FLAGS_test_bin_name, bin_dir + "/utils/dns_server",
+        bin_dir + "/resolver_test_record_groups.yaml",
+        bin_dir + "/utils/dns_resolver", bin_dir + "/utils/tcp_connect");
   } else {
     // Get the current binary's directory relative to repo root to invoke the
     // correct build config (asan/tsan/dbg, etc.).
@@ -180,8 +185,10 @@ int main(int argc, char** argv) {
     grpc::testing::InvokeResolverComponentTestsRunner(
         "test/cpp/naming/resolver_component_tests_runner.sh",
         bin_dir + "/" + FLAGS_test_bin_name,
-        "test/cpp/naming/test_dns_server.py",
-        "test/cpp/naming/resolver_test_record_groups.yaml");
+        "test/cpp/naming/utils/dns_server.py",
+        "test/cpp/naming/resolver_test_record_groups.yaml",
+        "test/cpp/naming/utils/dns_resolver.py",
+        "test/cpp/naming/utils/tcp_connect.py");
   }
   grpc_shutdown();
   return 0;

test/cpp/naming/utils/BUILD

@@ -0,0 +1,50 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+package(
+    default_visibility = ["//visibility:public"],
+    features = [
+        "-layering_check",
+        "-parse_headers",
+    ],
+)
+
+licenses(["notice"])  # Apache v2
+
+load("//bazel:grpc_build_system.bzl", "grpc_py_binary")
+
+grpc_py_binary(
+  name = "dns_server",
+  srcs = ["dns_server.py"],
+  testonly = True,
+  external_deps = [
+      "twisted",
+      "yaml",
+  ]
+)
+
+grpc_py_binary(
+  name = "dns_resolver",
+  srcs = ["dns_resolver.py"],
+  testonly = True,
+  external_deps = [
+      "twisted",
+  ]
+)
+
+grpc_py_binary(
+  name = "tcp_connect",
+  srcs = ["tcp_connect.py"],
+  testonly = True,
+)

test/cpp/naming/utils/dns_resolver.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python2.7
+# Copyright 2015 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Makes DNS queries for A records to specified servers"""
+
+import argparse
+import signal
+import twisted.internet.task as task
+import twisted.names.client as client
+
+def main():
+  argp = argparse.ArgumentParser(description='Make DNS queries for A records')
+  argp.add_argument('-s', '--server_host', default='127.0.0.1', type=str,
+                    help='Host for DNS server to listen on for TCP and UDP.')
+  argp.add_argument('-p', '--server_port', default=53, type=int,
+                    help='Port that the DNS server is listening on.')
+  argp.add_argument('-n', '--qname', default=None, type=str,
+                    help=('Name of the record to query for. '))
+  argp.add_argument('-t', '--timeout', default=1, type=int,
+                    help=('Force process exit after this number of seconds.'))
+  args = argp.parse_args()
+  signal.alarm(args.timeout)
+  def OnResolverResultAvailable(result):
+    answers, authority, additional = result
+    for a in answers:
+      print(a.payload)
+  def BeginQuery(reactor, qname):
+    servers = [(args.server_host, args.server_port)]
+    resolver = client.Resolver(servers=servers)
+    deferred_result = resolver.lookupAddress(args.qname)
+    deferred_result.addCallback(OnResolverResultAvailable)
+    return deferred_result
+  task.react(BeginQuery, [args.qname])
+
+if __name__ == '__main__':
+  main()

test/cpp/naming/utils/tcp_connect.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python2.7
+# Copyright 2015 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Opens a TCP connection to a specified server and then exits."""
+
+import argparse
+import signal
+import socket
+
+def main():
+  argp = argparse.ArgumentParser(description='Open a TCP handshake to a server')
+  argp.add_argument('-s', '--server_host', default=None, type=str,
+                    help='Server host name or IP.')
+  argp.add_argument('-p', '--server_port', default=0, type=int,
+                    help='Port that the server is listening on.')
+  argp.add_argument('-t', '--timeout', default=1, type=int,
+                    help='Force process exit after this number of seconds.')
+  args = argp.parse_args()
+  signal.alarm(args.timeout)
+  socket.create_connection([args.server_host, args.server_port])
+
+if __name__ == '__main__':
+  main()