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A simple, minimalistic websocket client using LibWebSocket
// Simple LibWebSockets test client
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include "libwebsocket/libwebsockets.h"
static int bExit;
static int bDenyDeflate = 1;
static int callback_test(struct lws* wsi, enum lws_callback_reasons reason, void *user, void* in, size_t len);
// Escape the loop when a SIGINT signal is received
static void onSigInt(int sig)
bExit = 1;
// The registered protocols
static struct lws_protocols protocols[] = {
"test-protocol", // Protocol name
callback_test, // Protocol callback
0, // Data size per session (can be left empty)
512, // Receive buffer size (can be left empty)
{ NULL, NULL, 0 } // Always needed at the end
// The extensions LWS supports, without them some requests may not be able to work
static const struct lws_extension extensions[] = {
"permessage-deflate; client_max_window_bits"
{ NULL, NULL, NULL } // Always needed at the end
// List to identify the indices of the protocols by name
enum protocolList {
// Callback for the test protocol
static int callback_test(struct lws* wsi, enum lws_callback_reasons reason, void *user, void* in, size_t len)
// The message we send back to the echo server
const char msg[128] = "Simple webserver echo test!";
// The buffer holding the data to send
// NOTICE: data which is sent always needs to have a certain amount of memory (LWS_PRE) preserved for headers
unsigned char buf[LWS_PRE + 128];
// Allocating the memory for the buffer, and copying the message to it
memset(&buf[LWS_PRE], 0, 128);
strncpy((char*)buf + LWS_PRE, msg, 128);
// For which reason was this callback called?
switch (reason)
// The connection closed
printf("[Test Protocol] Connection closed.\n");
// Our client received something
printf("[Test Protocol] Received data: \"%s\"\n", (char*)in);
bExit = 1;
return -1; // Returning -1 causes the client to disconnect from the server
// Here the server tries to confirm if a certain extension is supported by the server
if (strcmp((char*)in, "deflate-stream") == 0)
if (bDenyDeflate)
printf("[Test Protocol] Denied deflate-stream extension\n");
return 1;
// The connection was successfully established
printf("[Test Protocol] Connection to server established.\n");
printf("[Test Protocol] Writing \"%s\" to server.\n", msg);
// Write the buffer from the LWS_PRE index + 128 (the buffer size)
lws_write(wsi, &buf[LWS_PRE], 128, LWS_WRITE_TEXT);
// The server notifies us that we can write data
printf("[Test Protocol] The client is able to write.\n");
// There was an error connecting to the server
printf("[Test Protocol] There was a connection error: %s\n", in ? (char*)in : "(no error information)");
return 0;
// Main application entry
int main()
lws_set_log_level(LLL_ERR | LLL_WARN, lwsl_emit_syslog); // We don't need to see the notice messages
signal(SIGINT, onSigInt); // Register the SIGINT handler
// Connection info
char inputURL[300] = "ws://";
int inputPort = 80;
struct lws_context_creation_info ctxCreationInfo; // Context creation info
struct lws_client_connect_info clientConnectInfo; // Client creation info
struct lws_context *ctx; // The context to use
struct lws *wsiTest; // WebSocket interface
const char *urlProtocol, *urlTempPath; // the protocol of the URL, and a temporary pointer to the path
char urlPath[300]; // The final path string
// Set both information to empty and allocate it's memory
memset(&ctxCreationInfo, 0, sizeof(ctxCreationInfo));
memset(&clientConnectInfo, 0, sizeof(clientConnectInfo));
clientConnectInfo.port = inputPort; // Set the client info's port to the input port
// Parse the input url (e.g. wss://
// the protocol (wss)
// the address (
// the port (1234)
// the path (/test)
if (lws_parse_uri(inputURL, &urlProtocol, &clientConnectInfo.address, &clientConnectInfo.port, &urlTempPath))
printf("Couldn't parse URL\n");
// Fix up the urlPath by adding a / at the beginning, copy the temp path, and add a \0 at the end
urlPath[0] = '/';
strncpy(urlPath + 1, urlTempPath, sizeof(urlPath) - 2);
urlPath[sizeof(urlPath) - 1] = '\0';
clientConnectInfo.path = urlPath; // Set the info's path to the fixed up url path
// Set up the context creation info
ctxCreationInfo.port = CONTEXT_PORT_NO_LISTEN; // We don't want this client to listen
ctxCreationInfo.protocols = protocols; // Use our protocol list
ctxCreationInfo.gid = -1; // Set the gid and uid to -1, isn't used much
ctxCreationInfo.uid = -1;
ctxCreationInfo.extensions = extensions; // Use our extensions list
// Create the context with the info
ctx = lws_create_context(&ctxCreationInfo);
if (ctx == NULL)
printf("Error creating context\n");
return 1;
// Set up the client creation info
clientConnectInfo.context = ctx; // Use our created context
clientConnectInfo.ssl_connection = 0; // Don't use SSL for this test = clientConnectInfo.address; // Set the connections host to the address
clientConnectInfo.origin = clientConnectInfo.address; // Set the conntections origin to the address
clientConnectInfo.ietf_version_or_minus_one = -1; // IETF version is -1 (the latest one)
clientConnectInfo.protocol = protocols[PROTOCOL_TEST].name; // We use our test protocol
clientConnectInfo.pwsi = &wsiTest; // The created client should be fed inside the wsi_test variable
printf("Connecting to %s://%s:%d%s \n\n", urlProtocol, clientConnectInfo.address, clientConnectInfo.port, urlPath);
// Connect with the client info
if (wsiTest == NULL)
printf("Error creating the client\n");
return 1;
// Main loop runs till bExit is true, which forces an exit of this loop
while (!bExit)
// LWS' function to run the message loop, which polls in this example every 50 milliseconds on our created context
lws_service(ctx, 50);
// Destroy the context
printf("\nDone executing.\n");
return 0;
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