library("rvest")
library("data.table")

url<- "http://uyeler.mynet.com/login/login.asp?rurl=http%3A%2F%2Ffinans.mynet.com%2Fborsa%2Fcanliborsa%2F&formname=finans#A"
session<-html_session(url)
form<- html_form(session)[[1]]

login<- set_values(form, "username" ="muharrem_babaogul_1991","password"="q1w2e3")
submit_form(session,login)

jumped<-jump_to(session,url = 'http://finans.mynet.com/borsa/canliborsa/#A')

page<- read_html(jumped)
page<-html_nodes(page,xpath='//*[@id="canliLeftColumn"]/div[3]/table')
page<-  html_table(page)
head(page[[1]])

[1] Hisse         Hisse         Hisse         Son           Alış
[6] Satış         %Fark         En Düşük      En Yüksek     AOF
[11] Hacim (Lot)   Hacim (TL)    Son İşlem     Ekle / Kaldır
<0 rows> (or 0-length row.names)