Võrgurakenduste protokollid 1

Http

The web protocol: how to send web data over the TCP connection. Read this detailed intro.

Small example (from the intro above):

Request:

    GET /path/file.html HTTP/1.0
    From: someuser@jmarshall.com
    User-Agent: HTTPTool/1.0
    [blank line here]

The server should respond with something like the following, sent back through the same socket:

    HTTP/1.0 200 OK
    Date: Fri, 31 Dec 1999 23:59:59 GMT
    Content-Type: text/html
    Content-Length: 1354

    <html>
    <body>
    <h1>Happy New Millennium!</h1>
    (more file contents)
      .
      .
      .
    </body>
    </html>

Http lisadetaile

Toore TCP suhtluse järgi näeb http välja selliselt.

Päring serverile

GET failipath HTTP/1.1
Host: masinkustparid
lisainfo1:lisainfovaartus1
lisainfo2:lisainfovaartus2

suvaline
tekst

kus

• failipath oleks näiteks /cgi-bin/prog?c=150&d=aaeeff jne
• GET asemel võib kasutada POST
• HTTP/1.1 asemel võib kasutada HTTP/1.0
• lisainfo:l... headeriridu ei ole üldjuhul vaja saata, vahel on neist kasu

Iga rea lõpus alguses kuni sisuni peab olema carriage return ja line feed paar, enne sisu peab olema tühi rida. GET päringu puhul sisu ei anta.

• HTTP/1.1 puhul on Host: väli kohustuslik, kuid sinna võib panna mida iganes
• HTTP/1.0 puhul ei ole Host: kohustuslik.

User-Agent: ei ole minu teada kohustuslik, aga seda võiks kasutada ja panna sinna nimeks sinu enda proge nimi. Tähtsust sellel väärtusel ei ole.

Terviknäide OK päringust:

GET /cgi-bin/prog?c=150&d=aaeeff HTTP/1.1
Host: dijkstra.cs.ttu.ee
User-Agent: minuproge

ja terviknäide veel lihtsamast HTTP/1.0 päringust:

GET /cgi-bin/progr?c=150&d=aaeeff HTTP/1.0
User-Agent: minuproge

Vastus serverilt:

HTTP/1.1 200 OK
lisainfo:lisainfovaartus
lisainfo:vaartus
Content-Length: 123
Content-Type: text/plain

vastus
tekst

Content-Length ei ole päris kohustuslik, kuid on mõistlik. Seda võib kasutada ntx selleks, et allokeerida piisavalt ruumi data jaoks.

Kui teha serverirakendus mõne olemasoleva http serveri külge, siis reeglina see serverirakendus ise annab välja headeri alguse read alates

HTTP/1.1 200 OK

ja sinna peaks rakendus lisama

Content-type: text/plain

ja võib ka (aga ei pea)

Content-Length: sisupikkus

ja seejärel trükkida tühi rida ja seejärel trükkida juba saadetav sisu.

Konkreetne vastusenäide serverilt:

HTTP/1.1 200 OK
Date: Sun, 13 Nov 2011 16:53:12 GMT
Server: Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.18 with Suhosin-Patch
Keep-Alive: timeout=15, max=97
Connection: Keep-Alive
Content-Length: 169
Content-Type: text/plain

sisu.....

Kus siis Content-Length: reani trükkis apache server ja alates Content-Length: 169 trükkis minu rakendus ning meid huvitav sisu algab peale esimest tühja rida.

Vaata ka:

• caching ja ETAG

https

Ehk kuidas käib krüpteeritud http:

https://medium.freecodecamp.org/https-explained-with-carrier-pigeons-7029d2193351

http2.0

Ehk kõvasti täiendusi:

https://hpbn.co/http2

Olulist eelmiselt lingilt:

• "HTTP/2 no longer needs multiple TCP connections to multiplex streams in parallel; each stream is split into many frames, which can be interleaved and prioritized. As a result, all HTTP/2 connections are persistent, and only one connection per origin is required, which offers numerous performance benefits."

• "Unless you are implementing a web server (or a custom client) by working with raw TCP sockets, then you won’t see any difference: all the new, low-level framing is performed by the client and server on your behalf. The only observable differences will be improved performance and availability of new capabilities like request prioritization, flow control, and server push! "

websockets

Raw links:

• https://en.wikipedia.org/wiki/WebSocket
• http://blog.teamtreehouse.com/an-introduction-to-websockets
• https://www.html5rocks.com/en/tutorials/websockets/basics/

Curl näited

Curl on väga kasulik käsurea-tööriist pluss C teek erinevate http päringute tegemiseks. Tal on väga palju võimalusi eri parameetreid sättida jne.

Curl normaalpäring

curl 'http://81.20.146.85/cgi-bin/prog?c=150&d=aaeeff'

Curl normaalpäring, kus vastuse headerid kirjutatakse faili headers.txt

curl 'http://81.20.146.85/cgi-bin/prog?c=150&d=aaeeff' -D headers.txt

Curl päring HTTP/1.0-ga
curl 'http://81.20.146.85/cgi-bin/prog?c=150&d=aaeeff' --http1.0

Curl päring, kus annad suvalise Host: headeri

curl 'http://81.20.146.85/cgi-bin/prog?c=150&d=45' -D suva.txt  -H "Host: aaa"

Ja sama HTTP/1.0ga

curl 'http://81.20.146.85/cgi-bin/prog?c=150&d=45' -D suva.txt - -H "Host: aaa" -http1.0

Get and post

• GET: all data sent is in the headers & URL. If your form has METHOD="GET" in its FORM tag, your server program will receive the encoded form input in the environment variable QUERY_STRING.

• POST: when sending, after headers comes text. If your form has METHOD="POST" in its FORM tag, your server program will receive the encoded form input on stdin. The server will NOT send you an EOF on the end of the data, instead you should use the environment variable CONTENT_LENGTH to determine how much data you should read from stdin.

Post answer reading example in C:

 if (getenv("CONTENT_LENGTH") == NULL ||
      sscanf(getenv("CONTENT_LENGTH"), "%d", &cl) != 1) {   
    data_error(NULL,"bad http format or missing content length received");      
    return 1;   
  }                   
  // Create space for content: 
  querybuf = malloc(cl + 1);
  if (querybuf == NULL) {
    data_error(NULL,"cannot malloc for http request: bad content length?");
    return 1;
  }
  // Read content:    
  c='a';
  for(i=0; i<cl && c!=EOF; i++) {
   c=fgetc(stdin);
   querybuf[i]=c; 
  }  
  querybuf[i]=0;

Json

JSON details and official spec:

• http://en.wikipedia.org/wiki/JSON
• http://en.wikipedia.org/wiki/JSONP
• http://www.json.org
• http://tools.ietf.org/html/rfc4627

JSON-RPC: http://json-rpc.org/wiki/specification