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WebSocket 可以实现双向通信，适合实时通信场景。本文介绍一下使用 C 语言开发 AWTK-WEB 应用程序，并用 WebSocket 与服务器通讯。

用 AWTK Designer 新建一个应用程序

先安装 AWTK Designer：

https://awtk.zlg.cn/web/index.html

1. 新建应用程序

这里假设应用程序的名称为 AwtkApplicationCWebSocket，后面会用到，如果使用其它名称，后面要做相应修改。

2. 编写代码

2.1 用 VSCode 打开目录 AwtkApplicationCWebSocket，并打开文件 src/pages/home_page.c。

使用其它文本编辑器或 IDE 也可以，推荐使用 VSCode，并开启 Copilot，将大幅提升开发效率。

VSCode下载地址：https://code.visualstudio.com

2.2 添加事件处理函数。可以参考下面的代码：

typedef struct _home_page_t {  widget_t* send;  widget_t* send_text;  widget_t* recv_text;  EMSCRIPTEN_WEBSOCKET_T sock;} home_page_t;
static home_page_t* home_page_create(widget_t* win) {  home_page_t* home_page = TKMEM_ZALLOC(home_page_t);
  assert(win != NULL);  assert(home_page != NULL);  if (home_page != NULL) {    home_page->send = widget_lookup(win, "send", TRUE);    assert(home_page->send != NULL);    home_page->send_text = widget_lookup(win, "send_text", TRUE);    assert(home_page->send_text != NULL);    home_page->recv_text = widget_lookup(win, "recv_text", TRUE);    assert(home_page->recv_text != NULL);  }
  return home_page;}
static ret_t home_page_destroy(home_page_t* home_page) {  if (home_page != NULL) {    emscripten_websocket_close(home_page->sock, 0, 0);    TKMEM_FREE(home_page);  }
  return RET_OK;}
bool WebSocketOpen(int eventType, const EmscriptenWebSocketOpenEvent* e, void* userData) {  home_page_t* home_page = (home_page_t*)userData;  return_value_if_fail(home_page != NULL, FALSE);
  widget_set_text_utf8(home_page->recv_text, "opened");
  /*  emscripten_websocket_send_utf8_text(e->socket, "hello on the other side");  char data[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};  emscripten_websocket_send_binary(e->socket, data, sizeof(data));  */
  return 0;}
bool WebSocketClose(int eventType, const EmscriptenWebSocketCloseEvent* e, void* userData) {  home_page_t* home_page = (home_page_t*)userData;  return_value_if_fail(home_page != NULL, FALSE);
  emscripten_websocket_delete(e->socket);  widget_set_text_utf8(home_page->recv_text, "closed");  home_page->sock = 0;
  return 0;}
bool WebSocketError(int eventType, const EmscriptenWebSocketErrorEvent* e, void* userData) {  home_page_t* home_page = (home_page_t*)userData;  return_value_if_fail(home_page != NULL, FALSE);
  widget_set_text_utf8(home_page->recv_text, "error");
  return 0;}
bool WebSocketMessage(int eventType, const EmscriptenWebSocketMessageEvent* e, void* userData) {  home_page_t* home_page = (home_page_t*)userData;  return_value_if_fail(home_page != NULL, FALSE);
  if (e->isText) {    widget_set_text_utf8(home_page->recv_text, (const char*)(e->data));  }
  return 0;}
static ret_t on_send(void* ctx, event_t* e) {  home_page_t* home_page = (home_page_t*)ctx;  return_value_if_fail(home_page != NULL, RET_BAD_PARAMS);
  if (home_page->sock > 0) {    char text[1024];    widget_get_text_utf8(home_page->send_text, text, sizeof(text) - 1);    if (text[0] != '\0') {      emscripten_websocket_send_utf8_text(home_page->sock, text);    }  }
  return RET_OK;}
EMSCRIPTEN_WEBSOCKET_T create_socket(void* user_data, const char* url) {  EmscriptenWebSocketCreateAttributes attr;  emscripten_websocket_init_create_attributes(&attr);
  attr.url = url;  attr.protocols = "binary,base64";  EMSCRIPTEN_WEBSOCKET_T socket = emscripten_websocket_new(&attr);
  emscripten_websocket_set_onopen_callback(socket, user_data, WebSocketOpen);  emscripten_websocket_set_onclose_callback(socket, user_data, WebSocketClose);  emscripten_websocket_set_onerror_callback(socket, user_data, WebSocketError);  emscripten_websocket_set_onmessage_callback(socket, user_data, WebSocketMessage);
  return socket;}
/** * 初始化窗口 */ret_t home_page_init(widget_t* win, void* ctx) {  (void)ctx;  const char* url = "ws://localhost:8090/";  home_page_t* home_page = home_page_create(win);  return_value_if_fail(win != NULL && home_page != NULL, RET_BAD_PARAMS);
  assert(emscripten_websocket_is_supported());
  home_page->sock = create_socket(home_page, url);  widget_on(home_page->send, EVT_CLICK, on_send, home_page);
  return RET_OK;}

注意：控件的名称一定要和 home_page.xml 保持一致。

3. 在 AWTK Designer 中，执行“打包” “编译” “模拟运行”

正常情况下可以看到如下界面：

点击“关闭”按钮，退出应用程序。

编写配置文件

具体格式请参考，特殊平台编译配置：

https://github.com/zlgopen/awtk/blob/master/docs/build_config.md

这里给出一个例子，可以在此基础上进行修改，该文件位于：

examples/AwtkApplicationCWebSocket/build.json

{  "name": "AwtkApplicationCWebSocket",  "version": "1.0",  "assets": "res/assets",  "vendor": "zlgopen",  "app_name": "org.zlgopen.AwtkApplicationCWebSocket",  "author": "[e-mail]",  "copyright": "Guangzhou ZHIYUAN Electronics Co.,Ltd.",  "themes":["default"],  "sources": [     "src/*.c",     "src/common/*.c",     "src/pages/*.c",     "src/*.h",     "src/common/*.h",     "src/pages/*.h"  ],  "web": {    "app_type": "c",    "assets": "design",    "config": {      "fontScale": "0.8",      "defaultFont": "sans"    }  }

编译 WEB 应用程序

进入 awtk-web 目录，不同平台使用不同的脚本编译：

• Windows 平台

./build_win32.sh examples/AwtkApplicationCWebSocket/build.json release

• Linux 平台

./build_linux.sh examples/AwtkApplicationCWebSocket/build.json release

• MacOS 平台

./build_mac.sh examples/AwtkApplicationCWebSocket/build.json release

请根据应用程序所在目录，修改配置文件的路径。

运行

1. 正常启动

./start_web.sh

2. 调试启动

start_web_debug.sh

3. 启动 websocket 服务器（先安装 nodejs)

进入 awtk-web 目录下的 tools/websocket，执行：

node websocket_echo_server.js

4. 用浏览器打开URL：

http://localhost:8080/AwtkApplicationCWebSocket