ezwebsocket

Simple Websocket Library that supports server and client written in C

Features:

Websocket server
Websocket client
Simple usage
Callbacks for Events (onopen, onclose, onmessage)
Passes all tests of autobahn test suite
No external dependencies except pthreads
reference counting for buffers and descriptors
MIT License

Installation:

download and extract
$> ./autogen.sh
$> ./configure --prefix=/usr
$> make
$> sudo make install

Websocket server example

compile with:

$> gcc example_server.c -lezwebsocket -o example_server

/**
 * \file      example_server.c
 * \author    Clemens Kresser
 * \date      Mar 22, 2017
 * \copyright Copyright 2017-2021 Clemens Kresser MIT License
 * \brief     simple server example
 *
 */

#include <stdio.h>
#include <unistd.h>
#include <websocket.h>
#include <string.h>

/**
 * \brief callback that will be called when a connection is established
 *
 * \param *websocketUserData Pointer to the websocket user data associated with this socket
 *                           (data passed by websocketServer_open)
 * \param *wsDesc Pointer to the websocket server descriptor
 * \param *connectionDesc Pointer to the connection descriptor
 *
 * \return NULL
 */
void* onOpen(void *websocketUserData, struct websocket_server_desc *wsDesc,
             struct websocket_connection_desc *connectionDesc)
{
  printf("%s()\n", __func__);

  //you can return user data here which is then
  //passed to onMessage as connectionUserData
  return NULL;
}

/**
 * \brief callback that will be called when a message is received
 *
 * \param *websocketUserData Pointer to the websocket user data (data passed by websocketServer_open)
 * \param *connectionDesc Pointer to the connection descriptor
 * \param *connectionUserData Pointer to the connection user data (data returned by onOpen callback)
 * \param dataType The data type of the message (WS_DATA_TYPE_TEXT or WS_DATA_TYPE_BINARY)
 * \param *msg Pointer to the message
 * \param len The length of the message
 *
 */
void onMessage(void *websocketUserData, struct websocket_connection_desc *connectionDesc, void *connectionUserData,
               enum ws_data_type dataType, void *msg, size_t len)
{
  printf("%s()\n", __func__);
  if(dataType == WS_DATA_TYPE_TEXT)
  {
    printf("received:%s\n", (char*)msg);
  }
  // echo the received data
  websocket_sendData(connectionDesc, dataType, msg, len);
}

/**
 * \brief callback that will be called when a connection is closed
 *
 * \param *wsDesc Pointer to the websocket descriptor
 * \param *websocketUserData Pointer to the websocket user data (data passed by websocketServer_open)
 * \param *connectionDesc Pointer to the connection descriptor
 * \param *connectionUserData Pointer to the connection user data (data returned by onOpen callback)
 *
 */
void onClose(struct websocket_server_desc *wsDesc, void *websocketUserData,
             struct websocket_connection_desc *connectionDesc, void *connectionUserData)
{
  printf("%s()\n", __func__);
}

int main(int argc, char *argv[])
{
  struct websocket_server_init websocketInit;
  struct websocket_server_desc *wsServerDesc;

  websocketInit.port = "9001";
  websocketInit.address = "0.0.0.0";
  websocketInit.ws_onOpen = onOpen;
  websocketInit.ws_onClose = onClose;
  websocketInit.ws_onMessage = onMessage;

  wsServerDesc = websocketServer_open(&websocketInit, NULL);
  if(wsServerDesc == NULL)
    return -1;

  for(;;)
  {
    sleep(1);
  }

  websocketServer_close(wsServerDesc);

  return 0;
}

Websocket client example

compile with:

$> gcc example_client.c -lezwebsocket -o example_client

/**
 * \file      example_client.c
 * \author    Clemens Kresser
 * \date      Nov 17, 2020
 * \copyright Copyright 2017-2021 Clemens Kresser MIT License
 * \brief     simple client example
 *
 */

#include <stdio.h>
#include <unistd.h>
#include <websocket.h>
#include <string.h>

/**
 * \brief callback that will be called when a connection is established
 *
 * \param *websocketUserData Pointer to the websocket user data associated with this socket
 *                           (data passed by websocketClient_open)
 * \param *connectionDesc Pointer to the connection descriptor
 *
 * \return NULL
 */
void* onOpen(void *websocketUserData, struct websocket_connection_desc *connectionDesc)
{
  printf("%s()\n", __func__);

  //you can return user data here which is then
  //passed to onMessage as userData
  return NULL;
}

/**
 * \brief callback that will be called when a message is received
 *
 * \param *websocketUserData Pointer to the websocket user data (data passed by websocketClient_open)
 * \param *connectionDesc Pointer to the connection descriptor
 * \param *connectionUserData Pointer to the connection user data (data returned by onOpen callback)
 * \param dataType The data type of the message (WS_DATA_TYPE_TEXT or WS_DATA_TYPE_BINARY)
 * \param *msg Pointer to the message
 * \param len The length of the message
 *
 */
void onMessage(void *websocketUserData, struct websocket_connection_desc *connectionDesc, void *connectionUserData,
               enum ws_data_type dataType, void *msg, size_t len)
{
  if(dataType == WS_DATA_TYPE_TEXT)
  {
    printf("received:%s\n", (char*)msg);
  }
}

/**
 * \brief callback that will be called when a connection is closed
 *
 * \param *websocketUserData Pointer to the websocket user data (data passed by websocketClient_open)
 * \param *connectionDesc Pointer to the connection descriptor
 * \param *connectionUserData Pointer to the connection user data (data returned by onOpen callback)
 *
 */
void onClose(void *websocketUserData, struct websocket_connection_desc *connectionDesc, void *connectionUserData)
{
  printf("%s()\n", __func__);
}

int main(int argc, char *argv[])
{
  struct websocket_client_init websocketInit;
  struct websocket_connection_desc *wsConnectionDesc;

  const char *sendText = "Hello World From Ezwebsocket";

  websocketInit.port = "9001";
  websocketInit.address = "127.0.0.1";
  websocketInit.ws_onOpen = onOpen;
  websocketInit.ws_onClose = onClose;
  websocketInit.ws_onMessage = onMessage;

  wsConnectionDesc = websocketClient_open(&websocketInit, NULL);
  if(wsConnectionDesc == NULL)
    return -1;

  for(unsigned long i = 0; i < 10; i++)
  {
    //send "Hello World From Ezwebsocket" every second
    websocket_sendData(wsConnectionDesc, WS_DATA_TYPE_TEXT, sendText, strlen(sendText) + 1);
    sleep(1);
  }

  websocketClient_close(wsConnectionDesc);

  return 0;
}

Running the Autobahn Tests

Prerequisites

Download the Autobahn docker image from:

https://hub.docker.com/r/crossbario/autobahn-testsuite/tags/

Websocket client Test

Create a directory for the binary:

$> mkdir -p tests/bin

Compile test with:

$> gcc tests/client_autobahn.c -lezwebsocket -o tests/bin/client_autobahn

Start autobahn docker image with:

$> cd tests && ./run_autobahn_client_test.sh

Start websocket test program with:

$> ./tests/bin/client_autobahn

You will then find the report at tests/reports/clients/index.html

Websocket Server Test