The complete program follows. It is generated from client-basic.c in the companion examples repository.

/*
 * client-basic.c -- minimal WebSocket client.
 *
 * Connects to a server, sends a text frame and a binary message, receives the
 * echoed reply for each, then disconnects. Point it at a running server-ws
 * (ws://localhost:8181/websocket).
 */

#include <vws/websocket.h>

#include "vwsx.h"

#include <stdio.h>

static const char* URI = "ws://localhost:8181/websocket";

/* Receive one echoed message, print it, and free it. */
static void recv_and_print(vws_cnx* cnx, const char* what)
{
    vws_msg* reply = vws_msg_recv(cnx);

    if (reply == NULL)
    {
        vwsx_die("vws_msg_recv() returned NULL waiting for %s", what);
    }

    /* The payload is reply->data->data (ucstr), length reply->data->size. */
    printf("client-basic: %s reply -- %zu bytes (opcode %u): %.*s\n",
           what,
           reply->data->size,
           reply->opcode,
           (int)reply->data->size,
           (const char*)reply->data->data);

    vws_msg_free(reply);
}

int main(void)
{
    /* vwsx_connect = vws_cnx_new + vws_connect, dying on failure. */
    vws_cnx* cnx = vwsx_connect(URI);

    /* Send a single text frame. */
    if (vws_frame_send_text(cnx, "hello over a text frame") < 0)
    {
        vwsx_die("vws_frame_send_text() failed");
    }
    recv_and_print(cnx, "text");

    /* Send a binary message. */
    const unsigned char payload[] = { 0x01, 0x02, 0x03, 0x04 };
    if (vws_msg_send_binary(cnx, (ucstr)payload, sizeof(payload)) < 0)
    {
        vwsx_die("vws_msg_send_binary() failed");
    }
    recv_and_print(cnx, "binary");

    /* Clean shutdown. */
    vws_disconnect(cnx);
    vws_cnx_free(cnx);

    return 0;
}