{"id":278,"date":"2020-04-05T23:12:09","date_gmt":"2020-04-05T21:12:09","guid":{"rendered":"http:\/\/tech.sosthe.sk\/?p=278"},"modified":"2020-04-05T23:18:47","modified_gmt":"2020-04-05T21:18:47","slug":"2-aplikacna-vrstva","status":"publish","type":"post","link":"http:\/\/tech.sosthe.sk\/index.php\/2020\/04\/05\/2-aplikacna-vrstva\/","title":{"rendered":"2.1.\u2002 Architekt\u00fary sie\u0165ov\u00fdch aplik\u00e1ci\u00ed"},"content":{"rendered":"<p>Je be\u017en\u00e9, \u017ee dve r\u00f4zne sie\u0165ov\u00e9 aplik\u00e1cie od r\u00f4znych v\u00fdrobcov, a pokojne aj na r\u00f4znych opera\u010dn\u00fdch syst\u00e9moch, spolu na internete norm\u00e1lne komunikuj\u00fa. Komunik\u00e1cia medzi \u013eubovo\u013en\u00fdmi dvoma spusten\u00fdmi programami je realizovan\u00e1 spr\u00e1vami, ktor\u00e9 si navz\u00e1jom vymie\u0148aj\u00fa. To, \u017ee si tieto programy rozumej\u00fa, umo\u017e\u0148uj\u00fa aplika\u010dn\u00e9 protokoly, ktor\u00e9 ur\u010duj\u00fa, ak\u00e9 spr\u00e1vy si maj\u00fa tieto aplik\u00e1cie posiela\u0165. Sta\u010d\u00ed, \u017ee t\u00fdmto spr\u00e1vam rozumej\u00fa iba tieto dva programy. Ostatn\u00e9 sie\u0165ov\u00e9 zariadenia na ceste nijako tieto spr\u00e1vy nesprac\u00favaj\u00fa ani neanalyzuj\u00fa (za norm\u00e1lnych okolnost\u00ed). V\u00fdvoj nov\u00fdch aplika\u010dn\u00fdch protokolov je teda \u00faplne nez\u00e1visl\u00fd od fungovania siete a prenosu spr\u00e1v v nej.<\/p>\n<p>Ka\u017ed\u00fd aplika\u010dn\u00fd sie\u0165ov\u00fd protokol definuje:<\/p>\n<ul>\n<li><em>typy spr\u00e1v<\/em>, ktor\u00e9 si programy posielaj\u00fa (po\u017eiadavky, odpovede, inform\u00e1cie, r\u00f4zne typy d\u00e1t)<\/li>\n<li><em>syntax spr\u00e1v<\/em>\u00a0ur\u010duj\u00facu, ako bud\u00fa jednotliv\u00e9 spr\u00e1vy vyzera\u0165, z \u010doho bud\u00fa zlo\u017een\u00e9 a ak\u00e9 hodnoty m\u00f4\u017eu jednotliv\u00e9 \u010dasti spr\u00e1vy obsahova\u0165<\/li>\n<li><em>s\u00e9mantiku spr\u00e1v<\/em>\u00a0predstavuj\u00facu v\u00fdznam jednotliv\u00fdch spr\u00e1v a inform\u00e1ci\u00ed v nich<\/li>\n<li>okolnosti, za ktor\u00fdch sa jednotliv\u00e9 spr\u00e1vy posielaj\u00fa<\/li>\n<\/ul>\n<p>Defin\u00edcia verejn\u00fdch aplika\u010dn\u00fdch protokolov je dan\u00e1 v ich vo\u013ene pr\u00edstupn\u00fdch RFC \u0161pecifik\u00e1ci\u00e1ch. S\u00fakromn\u00e9 aplika\u010dn\u00e9 protokoly neumo\u017e\u0148uj\u00fa v\u00fdvoj nov\u00fdch koncov\u00fdch programov a ako serverov\u00fa, tak aj klientsku \u010das\u0165 mus\u00ed zabezpe\u010di\u0165 jeden program\u00e1tor (alebo skupina program\u00e1torov, ktor\u00e1 sa na danom protokole dohodla).<\/p>\n<p>Pred samotn\u00fdm p\u00edsan\u00edm nov\u00e9ho protokolu je potrebn\u00e9 si uvedomi\u0165, ak\u00fa rolu bud\u00fa hra\u0165 jednotliv\u00e9 \u010dasti sie\u0165ovej aplik\u00e1cie. Sie\u0165ov\u00e9 aplik\u00e1cie sa z tohto poh\u013eadu daj\u00fa rozdeli\u0165 na tri skupiny:<\/p>\n<ul>\n<li><strong>klient\/server architekt\u00fara<\/strong>\n<ul>\n<li>Predpoklad\u00e1, \u017ee na internete je jeden alebo viac st\u00e1le zapnut\u00fdch po\u010d\u00edta\u010dov s pevnou IP adresou naz\u00fdvan\u00fdch\u00a0<strong>servery<\/strong>. Na t\u00fdchto po\u010d\u00edta\u010doch be\u017e\u00ed\u00a0<strong>serverov\u00e1 \u010das\u0165 sie\u0165ovej aplik\u00e1cie<\/strong>.\u00a0<strong>Klienti<\/strong>\u00a0sp\u00fa\u0161\u0165aj\u00fa a vyp\u00ednaj\u00fa\u00a0<strong>klientsku \u010das\u0165 sie\u0165ovej aplik\u00e1cie<\/strong>\u00a0pod\u013ea potreby. M\u00f4\u017eu ma\u0165 dynamick\u00fa IP adresu, m\u00f4\u017eu sa tie\u017e nach\u00e1dza\u0165 v priv\u00e1tnej sieti za NAT routrom. Klienti komunikuj\u00fa v\u017edy iba so serverom, nikdy nie s ostatn\u00fdmi klientmi. Server mus\u00ed by\u0165 \u010dasto v\u00fdkonn\u00fd po\u010d\u00edta\u010d alebo dokonca klaster nieko\u013ek\u00fdch serverov, aby zvl\u00e1dol n\u00e1por mno\u017estva klientov.<\/li>\n<li>napr\u00edklad web servery, ftp servery, DNS servery, AiS2<\/li>\n<\/ul>\n<\/li>\n<li><strong>peer-to-peer architekt\u00fara<\/strong>\n<ul>\n<li>\u017diaden z po\u010d\u00edta\u010dov nemus\u00ed by\u0165 st\u00e1le zapnut\u00fd. Peer-ovia s\u00fa niekedy klientmi, niekedy servermi a \u010dasto oboma naraz. M\u00f4\u017eu sa odp\u00e1ja\u0165 a prip\u00e1ja\u0165 pod\u013ea \u013eubov\u00f4le. Z\u00e1\u0165a\u017e je rozlo\u017een\u00e1 ove\u013ea rovnomernej\u0161ie ako v pr\u00edpade klient\/server architekt\u00fary. Mana\u017eovanie siete je dos\u0165 \u0165a\u017ek\u00e9.<\/li>\n<li>napr\u00edklad Gnutella, Freenet<\/li>\n<\/ul>\n<\/li>\n<li><strong>Hybrid klient\/server a peer-to-peer architekt\u00fary<\/strong>\n<ul>\n<li>St\u00e1le zapnut\u00fd server sa pou\u017e\u00edva iba na registr\u00e1ciu a vyh\u013ead\u00e1vanie napojen\u00fdch peerov, pr\u00edpadne indexovanie ich d\u00e1t. Samotn\u00e9 nosn\u00e9 d\u00e1tov\u00e9 prenosy sa dej\u00fa u\u017e medzi jednotliv\u00fdmi peermi.<\/li>\n<li>napr\u00edklad Jabber, Skype, BitTorrent, DCC<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Je be\u017en\u00e9, \u017ee dve r\u00f4zne sie\u0165ov\u00e9 aplik\u00e1cie od r\u00f4znych v\u00fdrobcov, a pokojne aj na r\u00f4znych opera\u010dn\u00fdch syst\u00e9moch, spolu na internete norm\u00e1lne komunikuj\u00fa. Komunik\u00e1cia medzi \u013eubovo\u013en\u00fdmi&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"_links":{"self":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/278"}],"collection":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/comments?post=278"}],"version-history":[{"count":2,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/278\/revisions"}],"predecessor-version":[{"id":280,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/posts\/278\/revisions\/280"}],"wp:attachment":[{"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/media?parent=278"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/categories?post=278"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/tech.sosthe.sk\/index.php\/wp-json\/wp\/v2\/tags?post=278"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}