c - 向服务器发送 WebSocket 消息

Question

我正在尝试使用一台设备的 API，但它使用的是带有强制 Origin header 的 WS 接口(interface)，这给我带来了麻烦。

在 Chrome 中，我可以在加载具有正确来源的页面时打开控制台、创建 WS 连接并毫无困难地发送/接收消息: 请注意，发送的消息(绿色)始终会被服务器确认。

仅供引用，如果我在不同页面上创建连接，会发生以下情况，这会导致 Origin header 不匹配，报告为 404:

为了回避这个问题，我转向了 C，因为无论如何我的程序的其余部分都是用 C 编写的。这是我现在拥有的代码，主要基于 this answer :

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <libwebsockets.h>

#define KGRN "\033[0;32;32m"
#define KCYN "\033[0;36m"
#define KRED "\033[0;32;31m"
#define KYEL "\033[1;33m"
#define KBLU "\033[0;32;34m"
#define KCYN_L "\033[1;36m"
#define KBRN "\033[0;33m"
#define RESET "\033[0m"

static int destroy_flag = 0;
static int connection_flag = 0;
static int writeable_flag = 0;

static void INT_HANDLER(int signo) {
    destroy_flag = 1;
}

struct session_data {
    int fd;
};

struct pthread_routine_tool {
    struct lws_context *context;
    struct lws *wsi;
};

static int websocket_write_back(struct lws *wsi_in, char *str, int str_size_in) 
{
    if (str == NULL || wsi_in == NULL)
        return -1;

    int n;
    int len;
    char *out = NULL;

    if (str_size_in < 1) 
        len = strlen(str);
    else
        len = str_size_in;

    out = (char *)malloc(sizeof(char)*(LWS_SEND_BUFFER_PRE_PADDING + len + LWS_SEND_BUFFER_POST_PADDING));
    //* setup the buffer*/
    memcpy (out + LWS_SEND_BUFFER_PRE_PADDING, str, len );
    //* write out*/
    n = lws_write(wsi_in, out + LWS_SEND_BUFFER_PRE_PADDING, len, LWS_WRITE_TEXT);

    printf(KBLU"[websocket_write_back] %s\n"RESET, str);
    //* free the buffer*/
    free(out);

    return n;
}


static int ws_service_callback(
                         struct lws *wsi,
                         enum lws_callback_reasons reason, void *user,
                         void *in, size_t len)
{

    switch (reason) {

        case LWS_CALLBACK_CLIENT_ESTABLISHED:
            printf(KYEL"[Main Service] Connect with server success.\n"RESET);
            connection_flag = 1;
            break;

        case LWS_CALLBACK_CLIENT_CONNECTION_ERROR:
            printf(KRED"[Main Service] Connect with server error.\n"RESET);
            destroy_flag = 1;
            connection_flag = 0;
            break;

        case LWS_CALLBACK_CLOSED:
            printf(KYEL"[Main Service] LWS_CALLBACK_CLOSED\n"RESET);
            destroy_flag = 1;
            connection_flag = 0;
            break;

        case LWS_CALLBACK_CLIENT_RECEIVE:
            printf(KCYN_L"[Main Service] Client recvived:%s\n"RESET, (char *)in);

            if (writeable_flag)
                destroy_flag = 1;

            break;
        case LWS_CALLBACK_CLIENT_WRITEABLE :
            printf(KYEL"[Main Service] On writeable is called. send byebye message\n"RESET);
            websocket_write_back(wsi, "{\"command\":\"subscribe\",\"identifier\":\"{\\\"channel\\\":\\\"DevicesChannel\\\",\\\"share_token\\\":\\\"D0E91\\\"}\"}", -1);
            websocket_write_back(wsi, "{\"command\":\"message\",\"identifier\":\"{\\\"channel\\\":\\\"DevicesChannel\\\",\\\"share_token\\\":\\\"D0E91\\\"}\",\"data\":\"{\\\"value\\\":100,\\\"action\\\":\\\"set_buzz\\\"}\"}", -1);
            writeable_flag = 1;
            break;

        default:
            break;
    }

    return 0;
}

static void *pthread_routine(void *tool_in)
{
    struct pthread_routine_tool *tool = tool_in;

    printf(KBRN"[pthread_routine] Good day. This is pthread_routine.\n"RESET);

    //* waiting for connection with server done.*/
    while(!connection_flag)
        usleep(1000*20);

    //*Send greeting to server*/ 
    lws_callback_on_writable(tool->wsi);

}

int main(void)
{
    //* register the signal SIGINT handler */
    struct sigaction act;
    act.sa_handler = INT_HANDLER;
    act.sa_flags = 0;
    sigemptyset(&act.sa_mask);
    sigaction( SIGINT, &act, 0);


    struct lws_context *context = NULL;
    struct lws_context_creation_info info;
    struct lws *wsi = NULL;
    struct lws_protocols protocol;

    memset(&info, 0, sizeof info);
    info.port = CONTEXT_PORT_NO_LISTEN;
    info.iface = NULL;
    info.protocols = &protocol;
    info.ssl_cert_filepath = NULL;
    info.ssl_private_key_filepath = NULL;
    info.extensions = lws_get_internal_extensions();
    info.gid = -1;
    info.uid = -1;
    info.options = 0;

    protocol.name  = "websockets";
    protocol.callback = &ws_service_callback;
    protocol.per_session_data_size = sizeof(struct session_data);
    protocol.rx_buffer_size = 0;
    protocol.id = 0;
    protocol.user = NULL;

    context = lws_create_context(&info);
    printf(KRED"[Main] context created.\n"RESET);

    if (context == NULL) {
        printf(KRED"[Main] context is NULL.\n"RESET);
        return -1;
    }


    wsi = lws_client_connect(context, "mobu1.herokuapp.com", 443, 1,
        "/cable", "mobu1.herokuapp.com", "link.motorbunny.com",
    if (wsi == NULL) {
        printf(KRED"[Main] wsi create error.\n"RESET);
        return -1;
    }

    printf(KGRN"[Main] wsi create success.\n"RESET);

    struct pthread_routine_tool tool;
    tool.wsi = wsi;
    tool.context = context;

    pthread_t pid;
    pthread_create(&pid, NULL, pthread_routine, &tool);
    pthread_detach(pid);

    while(!destroy_flag)
    {
        lws_service(context, 50);
    }

    lws_context_destroy(context);

    return 0;
}

运行上述程序的结果是这样的:

如您所见，正在接收从服务器到客户端的定期 ping，但 lws_callback_on_writable(wsi); 似乎没有任何效果，因为 LWS_CALLBACK_CLIENT_WRITEABLE回调永远不会被调用。此外，如果我在其他地方直接调用 websocket_write_back()，它似乎不会向服务器发送任何内容，也不会出现任何确认。

我做错了什么明显的事情吗？

编辑1:我发现了这个简洁的 wscat，我可以在其中复制 Chrome 的结果: 现在的问题是，我如何才能将它与我的 C 程序连接起来，使其可以等待来自服务器的欢迎消息，然后发送两条消息？更好的是，如何保持连接，以便我的程序可以在不同时间点发送多个命令，而不必一直进行握手？

Answer 1

LWS_CALLBACK_CLIENT_WRITEABLE 回调从未被调用的原因是该特定服务器使用非标准握手。所以，为了绕过这个，我 forked libwsclient 的一个分支，并修改了握手检查功能，使其不会因不匹配而失败。我还添加了一个可选的 Origin header 。

现在，我在原来的程序中需要做的就是

wsclient *client;
char sync_str[6];
void mb_send(int power, char* type)
{
  char cmd[2048];
  sprintf (cmd, "{\"command\":\"message\",\"identifier\":\"{\\\"channel\\\":\\\"DevicesChannel\\\",\\\"share_token\\\":\\\"%s\\\"}\",\"data\":\"{\\\"value\\\":%d,\\\"action\\\":\\\"set_%s\\\"}\"}",sync_str,power,type);
  libwsclient_send(client,cmd);
}
void mb_connect()
{
  char cmd[2048];
  sprintf (cmd, "{\"command\":\"subscribe\",\"identifier\":\"{\\\"channel\\\":\\\"DevicesChannel\\\",\\\"share_token\\\":\\\"%s\\\"}\"}",sync_str);
  libwsclient_send(client,cmd);
  mb_send(0,"buzz");
}
int nop()
{
  return 0;
}
int main()
{
  client = libwsclient_new_extra("wss://mobu1.herokuapp.com/cable","https://link.motorbunny.com");
  if(!client) {
    fprintf(stderr, "Unable to initialize new WS client.\n");
    exit(1);
  }

  libwsclient_onopen(client, &nop);
  libwsclient_onmessage(client, &nop);
  libwsclient_onerror(client, &nop);
  libwsclient_onclose(client, &nop);

  libwsclient_run(client);

  ...
  mb_connect();
  ...  
  mb_send(200,"buzz");
  mb_send(40,"twirl");
  ...
  mb_send(0,"buzz");
  mb_send(0,"twirl");
}