Mfcttrf

I am trying to build some kind of a tree, but in its node instead of a symbol I want to put a framebox. Also, in that framebox at a specific position I want an other framebox. While I couldn't find a way to use the tree structure that exists in latex in order to do so, I started putting frameboxes at the positions that I wanted. Thus, I built the following, but now I don't know how too draw a line that connects each bi to the s.

beginfigure

setlengthunitlength0.06in
centering

beginpicture(70,50)

put(25,35)framebox(14,10)Large server 
put(0,5)framebox(14,10)Large browser 1
put(25,5)framebox(14,10)Large browser 2
put(50,5)framebox(14,10)Large browser 3
put(30.5,35)framebox(3,3)s
put(5.5,12)framebox(3,3)$b_1$
put(30.5,12)framebox(3,3)$b_2$
put(55.5,12) framebox(3,3)$b_3$

endpicture 
endfigure

Like this?

with forest and using nodes' labels is simple:

documentclass[border=1cm]standalone
usepackage[edges]forest

tikzsetevery label/.append style = draw, inner sep=2pt
begindocument
beginforest
for tree = 
 draw,
 text width=22mm, minimum height=16mm,
 font=Large,
 text centered,
 parent anchor=south,
 child anchor=north,
 %
 l sep=8mm,
 s sep=6mm,
 
[server, label=[anchor=south]below:s
 [browser 1, label=[anchor=north]:$b_1$]
 [browser 2, label=[anchor=north]:$b_2$]
 [browser 3, label=[anchor=north]:$b_3$]
]
endforest
enddocument

With pict2e you can easily draw segments specifying their end points.

documentclassarticle
usepackagepict2e

begindocument

beginfigure

setlengthunitlength0.06in
centering

beginpicture(70,50)
put(25,35)framebox(14,10)Large server 
put(0,5)framebox(14,10)Large browser 1
put(25,5)framebox(14,10)Large browser 2
put(50,5)framebox(14,10)Large browser 3
put(30.5,35)framebox(3,3)s
put(5.5,12)framebox(3,3)$b_1$
put(30.5,12)framebox(3,3)$b_2$
put(55.5,12) framebox(3,3)$b_3$
Line(7,15)(32,35)
Line(32,15)(32,35)
Line(57,15)(32,35)
endpicture 

endfigure

enddocument