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
• $> meson build_dir -D openssl=true -D examples=false
• $> cd build_dir
• $> ninja
• $> sudo ninja 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

Create a directory for the binary:

$> mkdir -p tests/bin

Compile test with:

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

Start websocket test program with:

$> ./tests/bin/server_autobahn

Start autobahn docker image with:

$> cd tests && ./run_autobahn_client_test.sh

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