The server class

Now, it's time to take a look at the way things are handled on the other side of the wire. Let's begin by defining some constants:

#define HEARTBEAT_INTERVAL 1000 // Milliseconds.
#define HEARTBEAT_RETRIES 5

Our server application is going to send out heartbeats every second and retry five times before it times out a client. Speaking of clients, there's additional information that we need to keep track of, which calls for a good data structure that holds it all:

struct ClientInfo{
   sf::IpAddress m_clientIP;
   PortNumber m_clientPORT;
   sf::Time m_lastHeartbeat;
   sf::Time m_heartbeatSent;
   bool m_heartbeatWaiting;
   unsigned short m_heartbeatRetry;
   unsigned int m_latency;

   ClientInfo(const sf::IpAddress& l_ip, const PortNumber& l_port,
     const sf::Time& l_heartbeat): m_clientIP(l_ip),
     m_clientPORT(l_port), m_lastHeartbeat(l_heartbeat), 
     m_heartbeatWaiting(false), m_heartbeatRetry(0), m_latency(0)
   {}

   ClientInfo&amp...