Libwebsocket 客户端示例
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【中文标题】Libwebsocket 客户端示例【英文标题】：Libwebsocket client example 【发布时间】：2015-06-18 00:16:27 【问题描述】：我试图找到一个示例来解释我如何使用 libwebsocket 实现客户端，但我没有得到任何令人信服的代码。有什么链接可以参考吗？
【问题讨论】：
【参考方案1】：更正了 Ren-Wei Luo 的代码示例以使用 libwebsockets 1.6
在 Ubuntu 14.04 上测试
example-server.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <libwebsockets.h>
#define KGRN "\033[0;32;32m"
#define KCYN "\033[0;36m"
#define KRED "\033[0;32;31m"
#define KYEL "\033[1;33m"
#define KMAG "\033[0;35m"
#define KBLU "\033[0;32;34m"
#define KCYN_L "\033[1;36m"
#define RESET "\033[0m"
static int destroy_flag = 0;
static void INT_HANDLER(int signo)
destroy_flag = 1;
/* *
* websocket_write_back: write the string data to the destination wsi.
*/
int websocket_write_back(struct lws *wsi_in, char *str, int str_size_in)
if (str == NULL || wsi_in == NULL)
return -1;
int n;
int len;
char *out = NULL;
if (str_size_in < 1)
len = strlen(str);
else
len = str_size_in;
out = (char *)malloc(sizeof(char)*(LWS_SEND_BUFFER_PRE_PADDING + len + LWS_SEND_BUFFER_POST_PADDING));
//* setup the buffer*/
memcpy (out + LWS_SEND_BUFFER_PRE_PADDING, str, len );
//* write out*/
n = lws_write(wsi_in, out + LWS_SEND_BUFFER_PRE_PADDING, len, LWS_WRITE_TEXT);
printf(KBLU"[websocket_write_back] %s\n"RESET, str);
//* free the buffer*/
free(out);
return n;
static int ws_service_callback(
struct lws *wsi,
enum lws_callback_reasons reason, void *user,
void *in, size_t len)
switch (reason)
case LWS_CALLBACK_ESTABLISHED:
printf(KYEL"[Main Service] Connection established\n"RESET);
break;
//* If receive a data from client*/
case LWS_CALLBACK_RECEIVE:
printf(KCYN_L"[Main Service] Server recvived:%s\n"RESET,(char *)in);
//* echo back to client*/
websocket_write_back(wsi ,(char *)in, -1);
break;
case LWS_CALLBACK_CLOSED:
printf(KYEL"[Main Service] Client close.\n"RESET);
break;
default:
break;
return 0;
struct per_session_data
int fd;
;
int main(void)
// server url will usd port 5000
int port = 5000;
const char *interface = NULL;
struct lws_context_creation_info info;
struct lws_protocols protocol;
struct lws_context *context;
// Not using ssl
const char *cert_path = NULL;
const char *key_path = NULL;
// no special options
int opts = 0;
//* register the signal SIGINT handler */
struct sigaction act;
act.sa_handler = INT_HANDLER;
act.sa_flags = 0;
sigemptyset(&act.sa_mask);
sigaction( SIGINT, &act, 0);
//* setup websocket protocol */
protocol.name = "my-echo-protocol";
protocol.callback = ws_service_callback;
protocol.per_session_data_size=sizeof(struct per_session_data);
protocol.rx_buffer_size = 0;
//* setup websocket context info*/
memset(&info, 0, sizeof info);
info.port = port;
info.iface = interface;
info.protocols = &protocol;
info.extensions = lws_get_internal_extensions();
info.ssl_cert_filepath = cert_path;
info.ssl_private_key_filepath = key_path;
info.gid = -1;
info.uid = -1;
info.options = opts;
//* create libwebsocket context. */
context = lws_create_context(&info);
if (context == NULL)
printf(KRED"[Main] Websocket context create error.\n"RESET);
return -1;
printf(KGRN"[Main] Websocket context create success.\n"RESET);
//* websocket service */
while ( !destroy_flag )
lws_service(context, 50);
usleep(10);
lws_context_destroy(context);
return 0;
example-client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <libwebsockets.h>
#define KGRN "\033[0;32;32m"
#define KCYN "\033[0;36m"
#define KRED "\033[0;32;31m"
#define KYEL "\033[1;33m"
#define KBLU "\033[0;32;34m"
#define KCYN_L "\033[1;36m"
#define KBRN "\033[0;33m"
#define RESET "\033[0m"
static int destroy_flag = 0;
static int connection_flag = 0;
static int writeable_flag = 0;
static void INT_HANDLER(int signo)
destroy_flag = 1;
struct session_data
int fd;
;
struct pthread_routine_tool
struct lws_context *context;
struct lws *wsi;
;
static int websocket_write_back(struct lws *wsi_in, char *str, int str_size_in)
if (str == NULL || wsi_in == NULL)
return -1;
int n;
int len;
char *out = NULL;
if (str_size_in < 1)
len = strlen(str);
else
len = str_size_in;
out = (char *)malloc(sizeof(char)*(LWS_SEND_BUFFER_PRE_PADDING + len + LWS_SEND_BUFFER_POST_PADDING));
//* setup the buffer*/
memcpy (out + LWS_SEND_BUFFER_PRE_PADDING, str, len );
//* write out*/
n = lws_write(wsi_in, out + LWS_SEND_BUFFER_PRE_PADDING, len, LWS_WRITE_TEXT);
printf(KBLU"[websocket_write_back] %s\n"RESET, str);
//* free the buffer*/
free(out);
return n;
static int ws_service_callback(
struct lws *wsi,
enum lws_callback_reasons reason, void *user,
void *in, size_t len)
switch (reason)
case LWS_CALLBACK_CLIENT_ESTABLISHED:
printf(KYEL"[Main Service] Connect with server success.\n"RESET);
connection_flag = 1;
break;
case LWS_CALLBACK_CLIENT_CONNECTION_ERROR:
printf(KRED"[Main Service] Connect with server error.\n"RESET);
destroy_flag = 1;
connection_flag = 0;
break;
case LWS_CALLBACK_CLOSED:
printf(KYEL"[Main Service] LWS_CALLBACK_CLOSED\n"RESET);
destroy_flag = 1;
connection_flag = 0;
break;
case LWS_CALLBACK_CLIENT_RECEIVE:
printf(KCYN_L"[Main Service] Client recvived:%s\n"RESET, (char *)in);
if (writeable_flag)
destroy_flag = 1;
break;
case LWS_CALLBACK_CLIENT_WRITEABLE :
printf(KYEL"[Main Service] On writeable is called. send byebye message\n"RESET);
websocket_write_back(wsi, "Byebye! See you later", -1);
writeable_flag = 1;
break;
default:
break;
return 0;
static void *pthread_routine(void *tool_in)
struct pthread_routine_tool *tool = tool_in;
printf(KBRN"[pthread_routine] Good day. This is pthread_routine.\n"RESET);
//* waiting for connection with server done.*/
while(!connection_flag)
usleep(1000*20);
//*Send greeting to server*/
printf(KBRN"[pthread_routine] Server is ready. send a greeting message to server.\n"RESET);
websocket_write_back(tool->wsi, "Good day", -1);
printf(KBRN"[pthread_routine] sleep 2 seconds then call onWritable\n"RESET);
sleep(1);
printf(KBRN"------------------------------------------------------\n"RESET);
sleep(1);
//printf(KBRN"[pthread_routine] sleep 2 seconds then call onWritable\n"RESET);
//*involked wriable*/
printf(KBRN"[pthread_routine] call on writable.\n"RESET);
lws_callback_on_writable(tool->wsi);
int main(void)
//* register the signal SIGINT handler */
struct sigaction act;
act.sa_handler = INT_HANDLER;
act.sa_flags = 0;
sigemptyset(&act.sa_mask);
sigaction( SIGINT, &act, 0);
struct lws_context *context = NULL;
struct lws_context_creation_info info;
struct lws *wsi = NULL;
struct lws_protocols protocol;
memset(&info, 0, sizeof info);
info.port = CONTEXT_PORT_NO_LISTEN;
info.iface = NULL;
info.protocols = &protocol;
info.ssl_cert_filepath = NULL;
info.ssl_private_key_filepath = NULL;
info.extensions = lws_get_internal_extensions();
info.gid = -1;
info.uid = -1;
info.options = 0;
protocol.name = "my-echo-protocol";
protocol.callback = &ws_service_callback;
protocol.per_session_data_size = sizeof(struct session_data);
protocol.rx_buffer_size = 0;
protocol.id = 0;
protocol.user = NULL;
context = lws_create_context(&info);
printf(KRED"[Main] context created.\n"RESET);
if (context == NULL)
printf(KRED"[Main] context is NULL.\n"RESET);
return -1;
wsi = lws_client_connect(context, "localhost", 5000, 0,
"/", "localhost:5000", NULL,
protocol.name, -1);
if (wsi == NULL)
printf(KRED"[Main] wsi create error.\n"RESET);
return -1;
printf(KGRN"[Main] wsi create success.\n"RESET);
struct pthread_routine_tool tool;
tool.wsi = wsi;
tool.context = context;
pthread_t pid;
pthread_create(&pid, NULL, pthread_routine, &tool);
pthread_detach(pid);
while(!destroy_flag)
lws_service(context, 50);
lws_context_destroy(context);
return 0;
制作文件
.PHONY:clean
all:example-client example-server
example-client:example-client.c
gcc example-client.c -o example-client -lpthread -lwebsockets
example-server:example-server.c
gcc example-server.c -o example-server -lwebsockets
clean:
-rm example-client example-server
【讨论】：
感谢您的示例！我在玩客户端示例，它在我身上出现了段错误：我的 1.7 版 libwebsockets 中的lws_context_creation_info info.protocols 字段需要一个 lws_protocols 数组，最后一个 lws_protocols 没有回调，否则在 context.c 中是一个 for 循环检查info->protocols[context->count_protocols].callback 溢出。如果有人发现这种情况发生在他们身上，只需制作一系列协议并确保最后一个没有回调。
警告读者info.protocols 需要一个以终止符(protocol.name == NULL) 结尾的数组。此处提供的示例并非如此。您也可能对libwebsockets.org/git/libwebsockets/tree/minimal-examples/… 的示例感兴趣
libwebsockets README 说明：“You should only send data on a websocket connection from the user callback LWS_CALLBACK_SERVER_WRITEABLE (or LWS_CALLBACK_CLIENT_WRITEABLE for clients).”...“您不能在 WRITEABLE 回调之外使用 lws_write() 发送数据”。当回调 reason 是 LWS_CALLBACK_RECEIVE 时，这里的服务器示例调用 lws_write() 不正确（但可能较旧的 libwebsockets 版本并没有阻止这一点）。
@zabumba 你能解释一下lws_service(context, 50);。是睡眠 50ms 吗？还是它会继续发送 ping/pong 消息以保持活力。【参考方案2】：
2021 年 11 月 1 日更新
最近几天，我收到了几个访问我以前在 Google Drive 上的 websocket 示例程序的请求。请注意，我在这篇文章中提到的示例写于 2015 年 8 月，其中 libwebsocket 库刚刚发布 1.5.0。我相信最新版本和 1.5.0 之间的机制肯定有很多变化。
从 2016 年开始，我改变了自己的职业道路，不再使用 C 语言进行编码。因此，我不知道如何修改示例代码以适应 libwebsocket 的最新机制。
如果您仍然对我的示例感兴趣，这里是the updated link to my google drive。
原帖
我使用纯 C 语言的 libwebsockets 编写了一个简单的回显服务器和客户端。
服务器端收到客户端的数据后会做回显。
连接建立后，客户端会向服务器写一个hello消息。然后在休眠 2 秒后，客户端会调用 libwebsocket_callback_on_writable。你可以看看它是如何工作的。
我只是将代码上传到我的 Google 驱动器上。
My google drive link
您可以在终端中使用以下命令编译代码。
gcc example-server.c -o example-server -lwebsockets
gcc example-client.c -o example-client -lpthread -lwebsockets
或者，只需在终端上使用 make。
【讨论】：
在 Ubuntu 14.04 上编译。我用 libwebsockets 1.6 试过这个，我得到example-client.c:64:61: error: parameter 3 (‘reason’) has incomplete type ...任何指针？
感谢您的正确 :D，libwebsocket 1.6 已将几乎所有变量的名称从 libwebsocket_* 更改为 lws_*。以上是关于Libwebsocket 客户端示例的主要内容，如果未能解决你的问题，请参考以下文章