參考Soket.IO官方文件：https://socket.io/docs/client-api/，客戶端內建事件一共有10種，事件如下：

socket.on('connect', function(data){
    //連線正常的事件
    console.log(JSON.stringify(data) + ' - connect');
});
socket.on('connect_error', function(data){
    console.log(JSON.stringify(data)+ ' - connect_error');
});
socket.on('connect_timeout', function(data){
    console.log(JSON.stringify(data)+ ' - connect_timeout');
});
socket.on('error', function(data){
    console.log(JSON.stringify(data) + ' - error');
});
socket.on('disconnect', function(data){
    //失去連線的事件
    console.log(JSON.stringify(data)+ ' - disconnect');
});
socket.on('reconnect', function(data){
    console.log(JSON.stringify(data) + ' - reconnect');
});
socket.on('reconnect_attempt', function(data){
    console.log(JSON.stringify(data)+ ' - reconnect_attempt');
});
socket.on('reconnecting', function(data){
    console.log(JSON.stringify(data)+ ' - reconnecting');
});
socket.on('reconnect_error', function(data){
    console.log(JSON.stringify(data)+ ' - reconnect_error');
});
socket.on('reconnect_failed', function(data){
    console.log(JSON.stringify(data)+ ' - reconnect_failed');
});
socket.on('ping', function(data){
    console.log(JSON.stringify(data)+ ' - ping');
});
socket.on('pong', function(data){
    console.log(JSON.stringify(data)+ ' - pong');
});
 

下圖是 斷網等異常情況下的內建事件流程