Add echo example apps to conduct end-to-end connectivity sanity check…

src/messaging/tests/echo/.gn

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+# Copyright (c) 2020 Project CHIP 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.
+
+# The location of the build configuration file.
+buildconfig = "//build/config/BUILDCONFIG.gn"
+
+# CHIP uses angle bracket includes.
+check_system_includes = true
+
+default_args = {
+  import("//args.gni")
+}

src/messaging/tests/echo/BUILD.gn

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+# Copyright (c) 2020 Project CHIP 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.
+
+import("//build_overrides/chip.gni")
+
+import("${chip_root}/build/chip/tools.gni")
+
+assert(chip_build_tools)
+
+executable("chip-echo-requester") {
+  sources = [
+    "common.cpp",
+    "echo_requester.cpp",
+  ]
+
+  public_deps = [
+    "${chip_root}/src/lib/core",
+    "${chip_root}/src/lib/support",
+    "${chip_root}/src/platform",
+    "${chip_root}/src/protocols",
+    "${chip_root}/src/system",
+  ]
+
+  if (is_debug) {
+    defines = [ "BUILD_RELEASE=0" ]
+  } else {
+    defines = [ "BUILD_RELEASE=1" ]
+  }
+
+  output_dir = root_out_dir
+}
+
+executable("chip-echo-responder") {
+  sources = [
+    "common.cpp",
+    "echo_responder.cpp",
+  ]
+
+  public_deps = [
+    "${chip_root}/src/lib/core",
+    "${chip_root}/src/lib/support",
+    "${chip_root}/src/platform",
+    "${chip_root}/src/protocols",
+    "${chip_root}/src/system",
+  ]
+
+  if (is_debug) {
+    defines = [ "BUILD_RELEASE=0" ]
+  } else {
+    defines = [ "BUILD_RELEASE=1" ]
+  }
+
+  output_dir = root_out_dir
+}
+
+group("echo") {
+  deps = [
+    ":chip-echo-requester",
+    ":chip-echo-responder",
+  ]
+}

src/messaging/tests/echo/README.md

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+# CHIP Example Application Tutorial
+
+## Introduction
+
+The CHIP Echo example application shows you how to implement a CHIP application
+program using one of the supported CHIP protocols, namely the very simple CHIP
+Echo protocol. This protocol allows you to send a CHIP message to a peer and
+expect a CHIP response (similar to the ICMP Echo Request/Echo Response
+messages).
+
+CHIP Protocols are, essentially, implementations of specific protocols over the
+CHIP transport. Furthermore, when two CHIP nodes are exchanging messages of a
+particular CHIP protocol, they do so over a construct called a CHIP Exchange
+which is a description of a CHIP-based conversation over a CHIP protocol. A CHIP
+Exchange is characterised by the ExchangeContext object, and every CHIP node
+must create an ExchangeContext object before initiating a CHIP conversation.
+
+After constructing a CHIP ExchangeContext, CHIP messages are sent and received
+using the ChipMessageLayer class which sends the CHIP message over a chosen
+transport (TCP, UDP, or CRMP).
+
+## Building
+
+```
+cd echo
+git submodule update --init
+source third_party/connectedhomeip/scripts/activate.sh
+gn gen out/debug
+ninja -C out/debug
+```
+
+-   After the applications are built, it can be found in the build directory as
+    `out/debug/chip-echo-requester and out/debug/chip-echo-responder`
+
+## Example Applications Walk Through
+
+As part of this example, we have a ChipEchoRequester program that acts as the
+client and sends echo requests to a ChipEchoResponder program that receives
+EchoRequests and sends back EchoResponse messages.
+
+### Ping a device over IP
+
+To start the Server in echo mode, run the built executable.
+
+    $ ./chip-echo-responder
+
+To start the Client in echo mode, run the built executable and pass it the IP
+address of the server to talk to.
+
+    $ ./chip-echo-requester <Server's IPv4 address>
+
+If valid values are supplied, it will begin to periodically send messages to the
+server address provided for three times.

src/messaging/tests/echo/args.gni

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+# Copyright (c) 2020 Project CHIP 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.
+
+import("//build_overrides/chip.gni")
+
+import("${chip_root}/config/standalone/args.gni")

src/messaging/tests/echo/build

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+third_party/connectedhomeip/build

src/messaging/tests/echo/build_overrides

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+../../../../examples/build_overrides

src/messaging/tests/echo/common.cpp

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+/*
+ *
+ *    Copyright (c) 2020 Project CHIP 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.
+ */
+
+/**
+ *    @file
+ *      This file implements constants, globals and interfaces common
+ *      to and used by CHIP example applications.
+ *
+ */
+
+#include <errno.h>
+
+#include "common.h"
+#include <support/ErrorStr.h>
+
+// The ExchangeManager global object.
+ExchangeManager gExchangeManager;
+
+void InitializeChip(void)
+{
+    CHIP_ERROR err = CHIP_NO_ERROR;
+
+    printf("Init CHIP Stack\r\n");
+
+    // Initialize System memory and resources
+    err = chip::Platform::MemoryInit();
+    SuccessOrExit(err);
+
+    // Initialize the CHIP stack.
+    err = chip::DeviceLayer::PlatformMgr().InitChipStack();
+    SuccessOrExit(err);
+
+exit:
+    if (err != CHIP_NO_ERROR)
+    {
+        printf("Failed to init CHIP Stack with err: %s\r\n", chip::ErrorStr(err));
+        exit(EXIT_FAILURE);
+    }
+}
+
+void ShutdownChip(void)
+{
+    gExchangeManager.Shutdown();
+    chip::DeviceLayer::SystemLayer.Shutdown();
+}
+
+void DriveIO(void)
+{
+    struct timeval sleepTime;
+    fd_set readFDs, writeFDs, exceptFDs;
+    int numFDs = 0;
+    int selectRes;
+
+    sleepTime.tv_sec  = 0;
+    sleepTime.tv_usec = NETWORK_SLEEP_TIME_MSECS;
+
+    FD_ZERO(&readFDs);
+    FD_ZERO(&writeFDs);
+    FD_ZERO(&exceptFDs);
+
+    if (chip::DeviceLayer::SystemLayer.State() == chip::System::kLayerState_Initialized)
+        chip::DeviceLayer::SystemLayer.PrepareSelect(numFDs, &readFDs, &writeFDs, &exceptFDs, sleepTime);
+
+    if (chip::DeviceLayer::InetLayer.State == chip::Inet::InetLayer::kState_Initialized)
+        chip::DeviceLayer::InetLayer.PrepareSelect(numFDs, &readFDs, &writeFDs, &exceptFDs, sleepTime);
+
+    selectRes = select(numFDs, &readFDs, &writeFDs, &exceptFDs, &sleepTime);
+    if (selectRes < 0)
+    {
+        printf("select failed: %s\n", chip::ErrorStr(chip::System::MapErrorPOSIX(errno)));
+        return;
+    }
+
+    if (chip::DeviceLayer::SystemLayer.State() == chip::System::kLayerState_Initialized)
+    {
+        chip::DeviceLayer::SystemLayer.HandleSelectResult(selectRes, &readFDs, &writeFDs, &exceptFDs);
+    }
+
+    if (chip::DeviceLayer::InetLayer.State == chip::Inet::InetLayer::kState_Initialized)
+    {
+        chip::DeviceLayer::InetLayer.HandleSelectResult(selectRes, &readFDs, &writeFDs, &exceptFDs);
+    }
+}

src/messaging/tests/echo/common.h

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+/*
+ *
+ *    Copyright (c) 2020 Project CHIP 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.
+ */
+
+/**
+ *    @file
+ *      This file defines some of the common constants, globals and interfaces
+ *      that are common to and used by CHIP example applications.
+ *
+ */
+
+#pragma once
+
+#include <core/CHIPCore.h>
+#include <messaging/ExchangeMgr.h>
+#include <platform/CHIPDeviceLayer.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <system/SystemPacketBuffer.h>
+#include <transport/SecureSessionMgr.h>
+#include <transport/raw/UDP.h>
+
+using namespace chip;
+
+#define MAX_MESSAGE_SOURCE_STR_LENGTH (100)
+#define NETWORK_SLEEP_TIME_MSECS (100 * 1000)
+
+constexpr chip::NodeId kClientDeviceId = 12344321;
+constexpr chip::NodeId kServerDeviceId = 12344322;
+
+extern ExchangeManager gExchangeManager;
+
+void InitializeChip(void);
+void ShutdownChip(void);
+void DriveIO(void);