Speed control in network

Under some circumstances you need to control the speed of sending or receiving data in network.

The speed of network is always measured by kbps, which means how many bits to send within one second.

Well, it’s like a physical exercise in high school. Speed == the amount of data / time interval

So there are two points we need to control: the amount of data and the time interval. And by controlling the two points we can control the speed.

There are two ways to implement speed control:

1, first we decide the time interval, after that we can count the max amount of bits to send within the period. And in each time period we send less data than the max amount.

It’s better to set time interval longer than one blocking sending time. The sending bytes works like a ruler, control the accuracy of speed control.

 

There is the sample code:

// global event to notify the arrival of time internal // initialized with non signal state QEvent g_event; #define  TIME_INTERNAL   200   void OnTimer(UINT nIDEvent) {     g_event.notify();     return; }   void startSendData() {     // first count the bytes to send per interval     int iRat = GetDlgItemInt(IDC_EDIT_RATE);//kbps     int iBytePerCP = iRat  * 1000 / 8 * TIME_INTERNAL / 1000;       // begin timer     SetTimer(NULL, TIME_INTERNAL, NULL);       // start sending thread     m_hTheadR = CreateThread(NULL, 0, readEmmThread, (LPVOID)&m_ThInof, NULL, NULL); }   // sending thread DWORD WINAPI sendEmmThread(LPVOID lpParameter) {     int iCountSended = 0;       while (TRUE) {          // send data...        iCountSended += send(...);          // for speed control        if (iCountSended >= iCountOnce) {              g_event.wait();            iCountSended = 0;        }     } }

 

2, if every send block have the same size, it’s no need to use a thread to send data, just send data in the OnTimer function. First decide how many bytes to send, then calculate time interval. Set timer and in OnTimer function send those bytes. But you must be sure within the interval all bytes can be send.

 

Each implement needs a timer, which to indicate begin of new interval. There are various types of timer which we may discuss later.

Of course you may use advanced technical such as QOS.