问题
I am trying to find a example which will explain me how to implement Client using libwebsocket, But I didn't get any convincing code. Is there any link that I can refer to?
回答1:
Corrected the code example by Ren-Wei Luo to work with libwebsockets 1.6
Tested on Ubuntu 14.04
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;
}
makefile
.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
回答2:
I have code a simple echo server and client using libwebsockets in pure C.
The server side will do echo after it received the data from client.
The client side will write a hello message to server after the connection is established. Then after 2 seconds sleep, the client will call libwebsocket_callback_on_writable. You can see how it works.
I just upload the code on my Google drive.
My google drive link
You can compile the code by using below commands in the Terminal.
gcc example-server.c -o example-server -lwebsockets
gcc example-client.c -o example-client -lpthread -lwebsockets
Or, just use make on Terminal.
来源：https://stackoverflow.com/questions/30904560/libwebsocket-client-example