linux下socket实现多个客户端向一个服务器端连续发送消息，服务器端使用MQTT转发消息

 

 左边同时启动了5个客户端，右边上面是server收界面client消息，右下方是mqtt subscruib 窗口。

本文的实现参考了几篇很不错的博客，下面列出给大家参考：

这是一个聊天室程序，实现多个客户端向一个服务端发送消息，服务端输入消息，可以向所有连接上的客户端广播。

• linux下socket编程实现一个服务器连接多个客户端

https://blog.csdn.net/zouli415/article/details/79696766 

• C++基础--完善Socket C/S ，实现客户端，服务器端断开重连     

https://blog.csdn.net/xqhrs232/article/details/51202118

• 在ubuntu上安装，使用MQTT Mosquitto

https://blog.csdn.net/usstmiracle/article/details/103050652

• Linux下学习用C语言实现MQTT(三）（异步函数）

https://blog.csdn.net/qq_43260665/article/details/88541433

 

talk is cheap show me the code!

socket通信 client.cpp 代码：

使用多线程实现了client断开重连。

#include     
#include 
#include     
#include     
#include     
#include     
#include     
#include 
#include 
  
#define BUFFER_SIZE 1024    


bool need_reconnect = false;    
//int main(int argc, const char * argv[])    
int client_connect(void) 
{    
    struct sockaddr_in server_addr;    
    server_addr.sin_family = AF_INET;    
    server_addr.sin_port = htons(11332);    
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); 
    //server_addr.sin_addr.s_addr = inet_addr("192.168.232.153");
  
    bzero(&(server_addr.sin_zero), 8);    
    //创建套接字
    int server_sock_fd = socket(AF_INET, SOCK_STREAM, 0);    
    if(server_sock_fd == -1)    
    {    
        perror("socket error");    
        return 1;    
    }    

    char recv_msg[BUFFER_SIZE];    
    char input_msg[BUFFER_SIZE];    
    //连接服务器
    if(connect(server_sock_fd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr_in)) == 0)    
    {   

        fd_set client_fd_set;    
        struct timeval tv;      
        while(1)    
        {    
            tv.tv_sec = 1;    
            tv.tv_usec = 0;    
            FD_ZERO(&client_fd_set);
            FD_SET(STDIN_FILENO, &client_fd_set);    
          //FD_SET(server_sock_fd, &client_fd_set);    
          
          //select(server_sock_fd += 1, &client_fd_set, NULL, NULL, &tv);    
           

            if(FD_ISSET(STDIN_FILENO, &client_fd_set))    
            {    
 
               bzero(input_msg, BUFFER_SIZE);    
              //fgets(input_msg, BUFFER_SIZE, stdin);
                strcpy(input_msg,"123456789 hello this test message Good news!!!!!!!!!!!");   
                //向服务端发送消息				
                if(send(server_sock_fd, input_msg, BUFFER_SIZE, 0) == -1)    
                {    
                    perror("Client send message error due to socket server program shutdown!\n");
                    need_reconnect = true;
                    return 0;    
                }
                need_reconnect = false;    
            }    
            if(FD_ISSET(server_sock_fd, &client_fd_set))    
            {    
                bzero(recv_msg, BUFFER_SIZE);
                //接收来自服务端的消息				
                long byte_num = recv(server_sock_fd, recv_msg, BUFFER_SIZE, 0);    
                if(byte_num > 0)    
                {    
                    if(byte_num > BUFFER_SIZE)    
                    {    
                        byte_num = BUFFER_SIZE;    
                    }    
                    recv_msg[byte_num] = '\0';    
                    printf("服务器:%s\n", recv_msg);    
                }else if(byte_num < 0)    
                {    
                    printf("接受消息出错!\n");    
                }else    
                {    
                    printf("服务器端退出!\n");    
                    exit(0);    
                }    
            }    
                
        }    
    }    
    return 0;    
}

void reconnect()
{
   int count =0;
   while(1)
  {
  
        if(need_reconnect)
        {
            client_connect();
            int left_time = (5-count);
            printf("reconnect 10s 1 times,left time: %d",left_time);
            count++;
        }
        sleep(10);

        if(count>4)
        {
           break;
        }
   }
 
   return;

}
   

int main(int argc, const char * argv[])    
{    
    std::thread th1(client_connect);

    std::thread th2(reconnect);

    th1.detach();

    th2.join();    
    
    return 0;    
} 

socket通信server.cpp和mqtt client publish的代码

#include    
#include    
#include    
#include    
#include    
#include    
#include  

//mqtt head file
#include "MQTTAsync.h"
#include 
#include 
  
#define BACKLOG 5          //完成三次握手但没有accept的队列的长度    
#define CONCURRENT_MAX 8   //应用层同时可以处理的连接    
#define SERVER_PORT 11332    
#define BUFFER_SIZE 1024    
#define QUIT_CMD ".quit"  

//mqtt define
#define ADDRESS     "tcp://localhost:1883"
#define CLIENTID    "clientPub"
#define TOPIC       "MQTT xxx"
//#define PAYLOAD     "Hello World!"
#define QOS         1
#define TIMEOUT     10000L
volatile MQTTAsync_token deliveredtoken;

int finished = 0;
bool is_connect = false;
long byte_num =0;
//socket 
int client_fds[CONCURRENT_MAX]; 
char input_msg[BUFFER_SIZE];    
char recv_msg[BUFFER_SIZE];

int rsu_server()
{
	std::mutex my_mutex;
	//本地地址    
    struct sockaddr_in server_addr;    
    server_addr.sin_family = AF_INET;    
    server_addr.sin_port = htons(SERVER_PORT);    
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");    
    bzero(&(server_addr.sin_zero), 8);    
    //创建socket    
    int server_sock_fd = socket(AF_INET, SOCK_STREAM, 0);    
    if(server_sock_fd == -1)    
    {    
        perror("socket error");    
        return 1;    
    }    
    //绑定socket    
    int bind_result = bind(server_sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr));    
    if(bind_result == -1)    
    {    
        perror("bind error");    
        return 1;    
    }    
    //listen    
    if(listen(server_sock_fd, BACKLOG) == -1)    
    {    
        perror("listen error");    
        return 1;    
    }    
    //fd_set    
    fd_set server_fd_set;    
    int max_fd = server_sock_fd;    
    struct timeval tv;  //超时时间设置
    while(1)    
    {    
        tv.tv_sec = 10;    
        tv.tv_usec = 0;    
        FD_ZERO(&server_fd_set); 
        //add standard input		
        FD_SET(STDIN_FILENO, &server_fd_set);    
       
        if(max_fd  0)    
                {    
                    int index = -1;    
                    for(int i = 0; i < CONCURRENT_MAX; i++)    
                    {    
                        if(client_fds[i] == 0)    
                        {    
                            index = i;    
                            client_fds[i] = client_sock_fd;    
                            break;    
                        }    
                    }    
                    if(index >= 0)    
                    {    
                        printf("新RSU客户端(%d)加入成功 %s:%d\n", index, inet_ntoa(client_address.sin_addr), ntohs(client_address.sin_port));    
                    }    
                    else    
                    {    
                        bzero(input_msg, BUFFER_SIZE);    
                        strcpy(input_msg, "服务器加入的RSU客户端数达到最大值,无法加入!\n");    
                        send(client_sock_fd, input_msg, BUFFER_SIZE, 0);    
                        printf("客户端连接数达到最大值，新RSU客户端加入失败 %s:%d\n", inet_ntoa(client_address.sin_addr), ntohs(client_address.sin_port));    
                    }    
                }    
            }
    
            for(int i =0; i < CONCURRENT_MAX; i++)    
            {    
                if(client_fds[i] !=0)    
                {    
                    if(FD_ISSET(client_fds[i], &server_fd_set))    
                    {    
                        //处理某个RSU客户端过来的消息-------------    
                        bzero(recv_msg, BUFFER_SIZE); 

			 //std::lock_guard lguard(my_mutex);
                         byte_num = recv(client_fds[i], recv_msg, BUFFER_SIZE, 0);    
                        if (byte_num > 0)    
                        {    
                            if(byte_num > (BUFFER_SIZE-4))    
                            {    
                                byte_num = (BUFFER_SIZE-4);    
                            }
                            recv_msg[byte_num++] = 'E';
                            recv_msg[byte_num++] = 'N';
                            recv_msg[byte_num++] = 'D';//添加消息的结尾标志
                            recv_msg[byte_num] = '\0';    
                            printf("RSU(%d):%s\n", i, recv_msg);    
                        }else if(byte_num < 0)    
                        {    
                            printf("从RSU(%d)接受消息出错.\n", i);    
                        } else    
                        {    
                            FD_CLR(client_fds[i], &server_fd_set);    
                            client_fds[i] = 0;    
                            printf("RSU客户端(%d)退出了\n", i);    
                        }    
                    }    
                }    
            }    
        }    
    }    
	return 0;
	
		
}	
//mqtt code -----------------------------------------------------



void connlost(void *context, char *cause)
{
	MQTTAsync client = (MQTTAsync)context;
	MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
	int rc;

	printf("\nConnection lost\n");
	printf("     cause: %s\n", cause);

	printf("Reconnecting\n");
	conn_opts.keepAliveInterval = 20;
	conn_opts.cleansession = 1;
	if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
	{
		printf("Failed to start connect, return code %d\n", rc);
 		finished = 1;
	}
}


void onDisconnect(void* context, MQTTAsync_successData* response)
{
	printf("Successful disconnection\n");
	finished = 1;
}


void onSend(void* context, MQTTAsync_successData* response)
{
	//MQTTAsync client = (MQTTAsync)context;
	//MQTTAsync_disconnectOptions opts = MQTTAsync_disconnectOptions_initializer;
	//int rc;

	printf("Message with token value %d delivery confirmed\n", response->token);
      
	//opts.onSuccess = onDisconnect;
	//opts.context = client;
        /* 
	if ((rc = MQTTAsync_disconnect(client, &opts)) != MQTTASYNC_SUCCESS)
	{
		printf("Failed to start sendMessage, return code %d\n", rc);
		exit(EXIT_FAILURE);
	}
          */
}


void onConnectFailure(void* context, MQTTAsync_failureData* response)
{
	printf("Connect broker failed, rc %d\n", response ? response->code : 0);
	finished = 1;
}


void onConnect(void* context, MQTTAsync_successData* response)
{
	MQTTAsync client = (MQTTAsync)context;
	MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
	MQTTAsync_message pubmsg = MQTTAsync_message_initializer;
	int rc;

	printf("Successful connection\n");
	is_connect = true;
/*	opts.onSuccess = onSend;
	opts.context = client;

	pubmsg.payload = (void*)PAYLOAD;
	pubmsg.payloadlen = (int)strlen(PAYLOAD);
	pubmsg.qos = QOS;
	pubmsg.retained = 0;
	deliveredtoken = 0;
        
	    if ((rc = MQTTAsync_sendMessage(client, TOPIC, &pubmsg, &opts)) != MQTTASYNC_SUCCESS)
	    {
		printf("Failed to start sendMessage, return code %d\n", rc);
		exit(EXIT_FAILURE);
	    }
*/        
}




int wuxi_server()
{    
	std::mutex mqtt_mutex;
	MQTTAsync client;
	MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
	int rc;
        char test_msg[100]="RSU client message is not arrived.This is the test information, please ignore it.";
	MQTTAsync_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);

	MQTTAsync_setCallbacks(client, NULL, connlost, NULL, NULL);

	conn_opts.keepAliveInterval = 20;
	conn_opts.cleansession = 1;
	conn_opts.onSuccess = onConnect;
	conn_opts.onFailure = onConnectFailure;
	conn_opts.context = client;
        
	if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
	{
		printf("Failed to start connect, return code %d\n", rc);
		exit(EXIT_FAILURE);
	}       
	printf("Waiting for publication of %s\n"
         "on topic %s for client with ClientID: %s\n",
         recv_msg, TOPIC, CLIENTID);
        while(!is_connect)
	{
	   //printf("sleep\n");
           usleep(100000L);
	}
        
	MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;  
        opts.onSuccess = onSend;
	opts.context = client;
        
        while(1)
	{	   
	   int rc;
           //printf("while1\n");
           //#define MQTTAsync_message_initializer 
	   MQTTAsync_message pubmsg = MQTTAsync_message_initializer;
	   //pubmsg.payload = (void*)PAYLOAD;
           
	   
           if(byte_num > 2)
           {        
               pubmsg.payload = (void*)recv_msg;
               pubmsg.payloadlen = (int)strlen(recv_msg);
           }else{
               pubmsg.payload = (void*)test_msg;
               pubmsg.payloadlen = (int)strlen(test_msg);
               usleep(2000000L); //（1ms = 1000us）  Send 1 times 2 second
           }

	   pubmsg.qos = QOS;
	   pubmsg.retained = 0;
	   deliveredtoken = 0;
           
	   if ((rc = MQTTAsync_sendMessage(client, TOPIC, &pubmsg, &opts)) != MQTTASYNC_SUCCESS)
	   {
		   printf("Failed to start sendMessage, return code %d\n", rc);
		   exit(EXIT_FAILURE);
	   }
	   std::lock_guard lguard(mqtt_mutex);
	   memset(recv_msg,0,sizeof(recv_msg));
           byte_num = 0; 
	   //usleep(20000L);//Send 50 times a second
           usleep(100000L);
	}

	while (!finished)
		#if defined(WIN32)
			Sleep(100);
		#else
			usleep(10000L);
		#endif

	MQTTAsync_destroy(&client);
 	return rc;
	
		
	
}


   
int main(int argc, const char * argv[])    
{    
    std::thread th1(rsu_server);

    std::thread th2(wuxi_server);

    th1.detach();

    th2.detach();

    while(1)
    {
       #if defined(WIN32)
		Sleep(100);
       #else
		usleep(1000000L);
       #endif
    }    
    
    return 0;    
}   

MQTT subscruib.cpp代码：

 

#include 
#include 
#include 
#include "MQTTAsync.h"
#include 


#define ADDRESS     "tcp://localhost:1883"
#define CLIENTID    "WXClientSub"
#define TOPIC       "MQTT YC2WX"
#define PAYLOAD     "Hello World!"
#define QOS         1
#define TIMEOUT     10000L

volatile MQTTAsync_token deliveredtoken;

int disc_finished = 0;
int subscribed = 0;
int finished = 0;

void connlost(void *context, char *cause)
{
	MQTTAsync client = (MQTTAsync)context;
	MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
	int rc;

	printf("\nConnection lost\n");
	if (cause)
		printf("     cause: %s\n", cause);

	printf("Reconnecting\n");
	conn_opts.keepAliveInterval = 20;
	conn_opts.cleansession = 1;
	if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
	{
		printf("Failed to start connect, return code %d\n", rc);
		finished = 1;
	}
}


int msgarrvd(void *context, char *topicName, int topicLen, MQTTAsync_message *message)
{
    int i;
    char* payloadptr;

    printf("Message arrived\n");
    printf("     topic: %s\n", topicName);
    printf("   message: ");

    payloadptr = (char*)message->payload;
    for(i=0; ipayloadlen; i++)
    {
        putchar(*payloadptr++);
    }
    putchar('\n');
    MQTTAsync_freeMessage(&message);
    MQTTAsync_free(topicName);
    return 1;
}


void onDisconnect(void* context, MQTTAsync_successData* response)
{
	printf("Successful disconnection\n");
	disc_finished = 1;
}


void onSubscribe(void* context, MQTTAsync_successData* response)
{
	printf("Subscribe succeeded\n");
	subscribed = 1;
}

void onSubscribeFailure(void* context, MQTTAsync_failureData* response)
{
	printf("Subscribe failed, rc %d\n", response ? response->code : 0);
	finished = 1;
}


void onConnectFailure(void* context, MQTTAsync_failureData* response)
{
	printf("Connect failed, rc %d\n", response ? response->code : 0);
	finished = 1;
}


void onConnect(void* context, MQTTAsync_successData* response)
{
	MQTTAsync client = (MQTTAsync)context;
	MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
	int rc;

	printf("Successful connection\n");

	printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
           "Press Q to quit\n\n", TOPIC, CLIENTID, QOS);
	opts.onSuccess = onSubscribe;
	opts.onFailure = onSubscribeFailure;
	opts.context = client;

	deliveredtoken = 0;

	if ((rc = MQTTAsync_subscribe(client, TOPIC, QOS, &opts)) != MQTTASYNC_SUCCESS)
	{
		printf("Failed to start subscribe, return code %d\n", rc);
		exit(EXIT_FAILURE);
	}
}


int main(int argc, char* argv[])
{
	MQTTAsync client;
	MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
	MQTTAsync_disconnectOptions disc_opts = MQTTAsync_disconnectOptions_initializer;
	int rc;
	int ch;

	MQTTAsync_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);

	MQTTAsync_setCallbacks(client, client, connlost, msgarrvd, NULL);

	conn_opts.keepAliveInterval = 20;
	conn_opts.cleansession = 1;
	conn_opts.onSuccess = onConnect;
	conn_opts.onFailure = onConnectFailure;
	conn_opts.context = client;
	if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
	{
		printf("Failed to start connect, return code %d\n", rc);
		exit(EXIT_FAILURE);
	}

	while	(!subscribed)
		#if defined(WIN32)
			Sleep(100);
		#else
			usleep(10000L);
		#endif

	if (finished)
		goto exit;

	do 
	{
		ch = getchar();
	} while (ch!='Q' && ch != 'q');

	disc_opts.onSuccess = onDisconnect;
	if ((rc = MQTTAsync_disconnect(client, &disc_opts)) != MQTTASYNC_SUCCESS)
	{
		printf("Failed to start disconnect, return code %d\n", rc);
		exit(EXIT_FAILURE);
	}
 	while	(!disc_finished)
		#if defined(WIN32)
			Sleep(100);
		#else
			usleep(10000L);
		#endif

exit:
	MQTTAsync_destroy(&client);
 	return rc;
}