1、HTML5新特性之WebSocket：
①HTTP协议的不足：基于“请求——响应”模型，只有在客户端发送请求后，服务器才会给予响应；对于实时的股票走势图，以及聊天通讯等无法满足需求；
②解决方案：setInterval+AJAX：心跳请求；
问题：过于频繁对服务器压力过大，频率过低则信息获取延迟；
③最佳解决方案——WebSocket协议：
基于“广播——收听”模型，客户端连接到服务器后不再断开，服务器有了消息随时发送给客户端，客户端也可以不停地给服务器发送消息；
不足：客户端和服务器是永久连接，服务器端可容纳的连接数是有限的；
④WebSocket应用需要服务器端和客户端都使用WebSocket协议；
⑤socket_server.php：
<?php
$address = "127.0.0.1";
$port = 9999; //调试的时候，可以多换端口来测试程序！
set_time_limit(0);
$sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_block($sock);
socket_bind($sock, $address, $port);
socket_listen($sock, 4);
do
{
echo "Waiting for Connection...\n";
$msgsock = socket_accept($sock);
echo "Waiting for Request...\n";
$buf = socket_read($msgsock, 8192); //读取请求
echo "Request Received: $buf\n";
$response = hand_shake($buf);
socket_write($msgsock,$response,strlen($response)); //发送响应
//正式开始通信...
$buf = socket_read($msgsock, 8192);
for($i=0; $i<5; $i++){
$msg = "WELCOME $i\n";
$msg = code($msg);
sleep(1);
socket_write($msgsock, $msg, strlen($msg));
}
socket_close($msgsock);
} while (true);
socket_close($sock);
function hand_shake($buf){
$buf = substr($buf,strpos($buf,‘Sec-WebSocket-Key:‘)+18);
$key = trim(substr($buf,0,strpos($buf,"\r\n")));
$new_key = base64_encode(sha1($key."258EAFA5-E914-47DA-95CA-C5AB0DC85B11",true));
$new_message = "HTTP/1.1 101 Switching Protocols\r\n";
$new_message .= "Upgrade: websocket\r\n";
$new_message .= "Sec-WebSocket-Version: 13\r\n";
$new_message .= "Connection: Upgrade\r\n";
$new_message .= "Sec-WebSocket-Accept: " . $new_key . "\r\n\r\n";
return $new_message;
}
function code($msg){
$msg = preg_replace(array(‘/\r$/‘,‘/\n$/‘,‘/\r\n$/‘,), ‘‘, $msg);
$frame = array();
$frame[0] = ‘81‘;
$len = strlen($msg);
$frame[1] = $len<16?‘0‘.dechex($len):dechex($len);
$frame[2] = ord_hex($msg);
$data = implode(‘‘,$frame);
return pack("H*", $data);
}
function ord_hex($data) {
$msg = ‘‘;
$l = strlen($data);
for ($i= 0; $i<$l; $i++) {
$msg .= dechex(ord($data{$i}));
}
return $msg;
}