程式語言 - GNU - C/C++ - LWS_SEND_BUFFER_PRE_PADDING + EXAMPLE_TX_BUFFER_BYTES + LWS_SEND_BUFFER_POST_PADDING

參考資訊：
https://github.com/iamscottmoyers/simple-libwebsockets-example

server.c

#include <stdio.h>
#include <string.h>
#include <libwebsockets.h>

#define EXAMPLE_RX_BUFFER_BYTES 255
#define LEN (LWS_SEND_BUFFER_PRE_PADDING + EXAMPLE_RX_BUFFER_BYTES + LWS_SEND_BUFFER_POST_PADDING)

struct payload {
    unsigned char data[LEN];
    size_t len;
} received_payload;

enum protocols {
    PROTOCOL_HTTP = 0,
    PROTOCOL_EXAMPLE,
    PROTOCOL_COUNT
};

static int callback_http(struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len)
{
    switch (reason) {
    case LWS_CALLBACK_HTTP:
        lws_serve_http_file(wsi, "main.htm", "text/html", NULL, 0);
        break;
    }

    return 0;
}

static int callback_example( struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len )
{
    switch (reason) {
    case LWS_CALLBACK_RECEIVE:
        memcpy(&received_payload.data[LWS_SEND_BUFFER_PRE_PADDING], in, len);
        received_payload.len = len;
        lws_callback_on_writable_all_protocol(lws_get_context(wsi), lws_get_protocol(wsi));
        break;
    case LWS_CALLBACK_SERVER_WRITEABLE:
        lws_write(wsi, &received_payload.data[LWS_SEND_BUFFER_PRE_PADDING], received_payload.len, LWS_WRITE_TEXT);
        break;
    }

    return 0;
}

static struct lws_protocols protocols[] =
{
    {
        "http-only",
        callback_http,
        0,
        0,
    },
    {
        "example-protocol",
        callback_example,
        0,
        EXAMPLE_RX_BUFFER_BYTES,
    },
    {
        NULL,
        NULL,
        0,
        0
    }
};

int main(int argc, char *argv[])
{
    struct lws_context_creation_info info = { 0 };

    info.port = 8000;
    info.protocols = protocols;
    info.gid = -1;
    info.uid = -1;

    struct lws_context *context = lws_create_context(&info);

    while (1) {
        lws_service(context, 1000000);
    }

    lws_context_destroy(context);

    return 0;
}

client.c

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

#define EXAMPLE_TX_BUFFER_BYTES 255
#define LEN (LWS_SEND_BUFFER_PRE_PADDING + EXAMPLE_TX_BUFFER_BYTES + LWS_SEND_BUFFER_POST_PADDING)

enum protocols {
    PROTOCOL_EXAMPLE = 0,
    PROTOCOL_COUNT
};

static struct lws *web_socket = NULL;

static int callback_example(struct lws *wsi, enum lws_callback_reasons reason, void *user, void *in, size_t len)
{
    size_t n = 0;
    unsigned char buf[LEN];
    unsigned char *p = &buf[LWS_SEND_BUFFER_PRE_PADDING];

    switch (reason) {
    case LWS_CALLBACK_CLIENT_ESTABLISHED:
        lws_callback_on_writable(wsi);
        break;
    case LWS_CALLBACK_CLIENT_WRITEABLE:
        n = sprintf((char *)p, "%s", "Hello, world!");
        lws_write(wsi, p, n, LWS_WRITE_TEXT);
        break;
    case LWS_CALLBACK_CLIENT_CLOSED:
    case LWS_CALLBACK_CLIENT_CONNECTION_ERROR:
        web_socket = NULL;
        break;
    }

    return 0;
}

static struct lws_protocols protocols[] = {
    {
        .name = "example-protocol",
        .callback = callback_example,
        .per_session_data_size = 0,
        .rx_buffer_size = 0,
        .id = 0,
        .user = NULL,
        .tx_packet_size = 0
    },
    {
        NULL,
        NULL,
        0,
        0
    }
};

int main(int argc, char *argv[])
{
    struct lws_context_creation_info info = { 0 };

    info.port = CONTEXT_PORT_NO_LISTEN;
    info.protocols = protocols;
    info.gid = -1;
    info.uid = -1;

    time_t old = 0;
    struct timeval tv;
    struct lws_context *context = lws_create_context(&info);

    while( 1 ) {
        gettimeofday(&tv, NULL);

        if (!web_socket && tv.tv_sec != old) {
            struct lws_client_connect_info ccinfo = { 0 };

            ccinfo.context = context;
            ccinfo.address = "localhost";
            ccinfo.port = 8000;
            ccinfo.path = "/";
            ccinfo.host = lws_canonical_hostname(context);
            ccinfo.origin = "origin";
            ccinfo.protocol = protocols[PROTOCOL_EXAMPLE].name;
            web_socket = lws_client_connect_via_info(&ccinfo);
        }

        if (tv.tv_sec != old) {
            lws_callback_on_writable(web_socket);
            old = tv.tv_sec;
        }

        lws_service(context, 250);
    }

    lws_context_destroy(context);

    return 0;
}

main.htm

<!DOCTYPE html>
<html>
<title>Websocket example</title>
<script>
    var socket = new WebSocket("ws://" + document.domain + ':' + location.port, "example-protocol");
    function update(msg) { document.getElementById("num").innerHTML = msg; }
    socket.onopen = function() { console.log("socket open"); update("open"); }
    socket.onclose = function() { console.log("socket close"); update("closed"); }
    socket.onmessage = function(msg) { console.log("socket message: " + msg.data); update(msg.data); }
</script>
<body>
    <p id="num"></p>
</body>
</html>

編譯、執行

$ gcc client.c -o client -lwebsockets
$ gcc client.c -o client -lwebsockets
$ ./server &
$ ./client &

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