C++ 实现TCP Socket心跳包的简易教程
最编程
2024-08-08 22:43:29
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在做游戏开发时,经常需要在应用层实现自己的心跳机制,即定时发送一个自定义的结构体(心跳包),让对方知道自己还活着,以确保连接的有效性。
在TCP socket心跳机制中,心跳包可以由服务器发送给客户端,也可以由客户端发送给服务器,不过比较起来,前者开销可能更大。—— 这里实现的是由客户端给服务器发送心跳包,基本思路是:
1) 服务器为每个客户端保存了IP和计数器count,即map<fd, pair<ip, count>>
。服务端主线程采用 select 实现多路IO复用,监听新连接以及接受数据包(心跳包),子线程用于检测心跳:
- 如果主线程接收到的是心跳包,将该客户端对应的计数器 count 清零;
- 在子线程中,每隔3秒遍历一次所有客户端的计数器 count:
- 若 count 小于 5,将 count 计数器加 1;
- 若 count 等于 5,说明已经15秒未收到该用户心跳包,判定该用户已经掉线;
2) 客户端则只是开辟子线程,定时给服务器发送心跳包(本示例中定时时间为3秒)。
下面是Linux下一个socket心跳包的简单实现:
/*************************************************************************
> File Name: Server.cpp
> Author: SongLee
> E-mail: lisong.shine@qq.com
> Created Time: 2016年05月05日 星期四 22时50分23秒
> Personal Blog: http://songlee24.github.io/
************************************************************************/
#include<netinet/in.h> // sockaddr_in
#include<sys/types.h> // socket
#include<sys/socket.h> // socket
#include<arpa/inet.h>
#include<unistd.h>
#include<sys/select.h> // select
#include<sys/ioctl.h>
#include<sys/time.h>
#include<iostream>
#include<vector>
#include<map>
#include<string>
#include<cstdlib>
#include<cstdio>
#include<cstring>
using namespace std;
#define BUFFER_SIZE 1024
enum Type {HEART, OTHER};
struct PACKET_HEAD
{
Type type;
int length;
};
void* heart_handler(void* arg);
class Server
{
private:
struct sockaddr_in server_addr;
socklen_t server_addr_len;
int listen_fd; // 监听的fd
int max_fd; // 最大的fd
fd_set master_set; // 所有fd集合,包括监听fd和客户端fd
fd_set working_set; // 工作集合
struct timeval timeout;
map<int, pair<string, int> > mmap; // 记录连接的客户端fd--><ip, count>
public:
Server(int port);
~Server();
void Bind();
void Listen(int queue_len = 20);
void Accept();
void Run();
void Recv(int nums);
friend void* heart_handler(void* arg);
};
Server::Server(int port)
{
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htons(INADDR_ANY);
server_addr.sin_port = htons(port);
// create socket to listen
listen_fd = socket(PF_INET, SOCK_STREAM, 0);
if(listen_fd < 0)
{
cout << "Create Socket Failed!";
exit(1);
}
int opt = 1;
setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
}
Server::~Server()
{
for(int fd=0; fd<=max_fd; ++fd)
{
if(FD_ISSET(fd, &master_set))
{
close(fd);
}
}
}
void Server::Bind()
{
if(-1 == (bind(listen_fd, (struct sockaddr*)&server_addr, sizeof(server_addr))))
{
cout << "Server Bind Failed!";
exit(1);
}
cout << "Bind Successfully.\n";
}
void Server::Listen(int queue_len)
{
if(-1 == listen(listen_fd, queue_len))
{
cout << "Server Listen Failed!";
exit(1);
}
cout << "Listen Successfully.\n";
}
void Server::Accept()
{
struct sockaddr_in client_addr;
socklen_t client_addr_len = sizeof(client_addr);
int new_fd = accept(listen_fd, (struct sockaddr*)&client_addr, &client_addr_len);
if(new_fd < 0)
{
cout << "Server Accept Failed!";
exit(1);
}
string ip(inet_ntoa(client_addr.sin_addr)); // 获取客户端IP
cout << ip << " new connection was accepted.\n";
mmap.insert(make_pair(new_fd, make_pair(ip, 0)));
// 将新建立的连接的fd加入master_set
FD_SET(new_fd, &master_set);
if(new_fd > max_fd)
{
max_fd = new_fd;
}
}
void Server::Recv(int nums)
{
for(int fd=0; fd<=max_fd; ++fd)
{
if(FD_ISSET(fd, &working_set))
{
bool close_conn = false; // 标记当前连接是否断开了
PACKET_HEAD head;
recv(fd, &head, sizeof(head), 0); // 先接受包头
if(head.type == HEART)
{
mmap[fd].second = 0; // 每次收到心跳包,count置0
cout << "Received heart-beat from client.\n";
}
else
{
// 数据包,通过head.length确认数据包长度
}
if(close_conn) // 当前这个连接有问题,关闭它
{
close(fd);
FD_CLR(fd, &master_set);
if(fd == max_fd) // 需要更新max_fd;
{
while(FD_ISSET(max_fd, &master_set) == false)
--max_fd;
}
}
}
}
}
void Server::Run()
{
pthread_t id; // 创建心跳检测线程
int ret = pthread_create(&id, NULL, heart_handler, (void*)this);
if(ret != 0)
{
cout << "Can not create heart-beat checking thread.\n";
}
max_fd = listen_fd; // 初始化max_fd
FD_ZERO(&master_set);
FD_SET(listen_fd, &master_set); // 添加监听fd
while(1)
{
FD_ZERO(&working_set);
memcpy(&working_set, &master_set, sizeof(master_set));
timeout.tv_sec = 30;
timeout.tv_usec = 0;
int nums = select(max_fd+1, &working_set, NULL, NULL, &timeout);
if(nums < 0)
{
cout << "select() error!";
exit(1);
}
if(nums == 0)
{
//cout << "select() is timeout!";
continue;
}
if(FD_ISSET(listen_fd, &working_set))
Accept(); // 有新的客户端请求
else
Recv(nums); // 接收客户端的消息
}
}
// thread function
void* heart_handler(void* arg)
{
cout << "The heartbeat checking thread started.\n";
Server* s = (Server*)arg;
while(1)
{
map<int, pair<string, int> >::iterator it = s->mmap.begin();
for( ; it!=s->mmap.end(); )
{
if(it->second.second == 5) // 3s*5没有收到心跳包,判定客户端掉线
{
cout << "The client " << it->second.first << " has be offline.\n";
int fd = it->first;
close(fd); // 关闭该连接
FD_CLR(fd, &s->master_set);
if(fd == s->max_fd) // 需要更新max_fd;
{
while(FD_ISSET(s->max_fd, &s->master_set) == false)
s->max_fd--;
}
s->mmap.erase(it++); // 从map中移除该记录
}
else if(it->second.second < 5 && it->second.second >= 0)
{
it->second.second += 1;
++it;
}
else
{
++it;
}
}
sleep(3); // 定时三秒
}
}
int main()
{
Server server(15000);
server.Bind();
server.Listen();
server.Run();
return 0;
}
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/*************************************************************************
> File Name: Client.cpp
> Author: SongLee
> E-mail: lisong.shine@qq.com
> Created Time: 2016年05月05日 星期四 23时41分56秒
> Personal Blog: http://songlee24.github.io/
************************************************************************/
#include<netinet/in.h> // sockaddr_in
#include<sys/types.h> // socket
#include<sys/socket.h> // socket
#include<arpa/inet.h>
#include<sys/ioctl.h>
#include<unistd.h>
#include<iostream>
#include<string>
#include<cstdlib>
#include<cstdio>
#include<cstring>
using namespace std;
#define BUFFER_SIZE 1024
enum Type {HEART, OTHER};
struct PACKET_HEAD
{
Type type;
int length;
};
void* send_heart(void* arg);
class Client
{
private:
struct sockaddr_in server_addr;
socklen_t server_addr_len;
int fd;
public:
Client(string ip, int port);
~Client();
void Connect();
void Run();
friend void* send_heart(void* arg);
};
Client::Client(string ip, int port)
{
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_family = AF_INET;
if(inet_pton(AF_INET, ip.c_str(), &server_addr.sin_addr) == 0)
{
cout << "Server IP Address Error!";
exit(1);
}
server_addr.sin_port = htons(port);
server_addr_len = sizeof(server_addr);
// create socket
fd = socket(AF_INET, SOCK_STREAM, 0);
if(fd < 0)
{
cout << "Create Socket Failed!";
exit(1);
}
}
Client::~Client()
{
close(fd);
}
void Client::Connect()
{
cout << "Connecting......" << endl;
if(connect(fd, (struct sockaddr*)&server_addr, server_addr_len) < 0)
{
cout << "Can not Connect to Server IP!";
exit(1);
}
cout << "Connect to Server successfully." << endl;
}
void Client::Run()
{
pthread_t id;
int ret = pthread_create(&id, NULL, send_heart, (void*)this);
if(ret != 0)
{
cout << "Can not create thread!";
exit(1);
}
}
// thread function
void* send_heart(void* arg)
{
cout << "The heartbeat sending thread started.\n";
Client* c = (Client*)arg;
int count = 0; // 测试
while(1)
{
PACKET_HEAD head;
head.type = HEART;
head.length = 0;
send(c->fd, &head, sizeof(head), 0);
sleep(3); // 定时3秒
++count; // 测试:发送15次心跳包就停止发送
if(count > 15)
break;
}
}
int main()
{
Client client("127.0.0.1", 15000);
client.Connect();
client.Run();
while(1)
{
string msg;
getline(cin, msg);
if(msg == "exit")
break;
cout << "msg\n";
}
return 0;
}
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可以看出,客户端启动以后发送了15次心跳包,然后停止发送心跳包。在经过一段时间后(3s*5),服务器就判断该客户端掉线,并断开了连接。