The handshake is simple: first a client connects to the server (usually port 80), then it sends a REQUEST. The server answers the REQUEST with a RESPONSE.
Since TCP/IP and ASCII is used, Telnet might be used to test a WWW-server (UNIX or Windows command: "telnet www.example.com 80"). A simple test is to connect with Telnet and then write "GET / HTTP/1.0" followed by TWO strokes on the RETURN-key of the keyboard. The server will then display the content of its "/index.html"-file in your TELNET-window. For a server hosting multiple domains at a single IP-number, such as a Web-hotell, you first type "GET / HTTP/1.1" followed by ONE stroke on the RETURN-key, then "Host: www.example.com" followed by TWO strokes on the RETURN-key.
It is fairly easy to write programs which are able to work as HTTP clients or servers. The main difficulty is to deal with the TCP/IP connections. Since the overhead is quite small, this means that HTTP-server implementations in embedded systems are very interesting alternatives to SNMP and other servers. With a build in HTTP-server embedded systems can be configured, polled for status, and so on, without any need for development of client software, networking, and complex client graphics programmes. It is possible to provide a small embedded system with a good and advanced networked MMI to low cost, short time, and small consumption of system memory.
fprintf(lanfp, "GET / HTTP/1.0\r\n"); /* Request line, first in the header (entity header) */
fprintf(lanfp, "Connection: Keep-Alive\r\n");
fprintf(lanfp, "User-Agent: Mozilla/3.0b4 (Win16; I)\r\n");
fprintf(lanfp, "Host: www.kalle.se:80\r\n");
fprintf(lanfp, "Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*\r\n");
fprintf(lanfp, "\r\n"); /* Empty line which finishes the header (entity header) */
fprintf(lanfp, "HTTP/1.0 200 OK\r\n"); /* Status line, first in the header (entity header) */
fprintf(lanfp, "Date: Friday, 28-Jun-96 10:23:49 GMT\r\n");
fprintf(lanfp, "Server: NCSA/1.3\r\n");
fprintf(lanfp, "MIME-version: 1.0\r\n");
fprintf(lanfp, "Content-type: text/html\r\n"); /* Type of data in enclosed file (entity body) */
fprintf(lanfp, "Last-modified: Monday, 17-Jun-96 11:17:33 GMT\r\n");
fprintf(lanfp, "Content-length: 4711\r\n"); /* Size of the enclosed file (entity body) */
fprintf(lanfp, "\r\n"); /* Empty line which finishes the header (entity header) */
fprintf(lanfp, "<HTML>\n"); /* First line in the enclosed file (entity body) */
fprintf(lanfp, " <HEAD>\n");
fprintf(lanfp, " <TITLE>Test document</TITLE>\n");
fprintf(lanfp, " </HEAD>\n");
fprintf(lanfp, " <BODY>\n");
fprintf(lanfp, " <H1>Test of HTTP</H1>\n\n");
fprintf(lanfp, " This document is used for tests with HTTP,\n");
.....
fprintf(lanfp, "GET / HTTP/1.0\r\n"); /* Request line, first in the header (entity header) */
fprintf(lanfp, "\r\n");
fprintf(lanfp, "HTTP/1.0 200 OK\r\n"); /* Status line, first in the header (entity header) */
fprintf(lanfp, "Content-type: text/html\r\n"); /* Type of data in enclosed file (entity body) */
fprintf(lanfp, "Content-length: 7849\r\n"); /* Size of the enclosed file (entity body) */
fprintf(lanfp, "\r\n"); /* Empty line which finishes the header (entity header) */
fprintf(lanfp, "<HTML>\n"); /* First line in the enclosed file (entity body) */
fprintf(lanfp, " <HEAD>\n");
fprintf(lanfp, " <TITLE>Test document</TITLE>\n");
fprintf(lanfp, " </HEAD>\n");
fprintf(lanfp, " <BODY>\n");
fprintf(lanfp, " <H1>Test of HTTP</H1>\n\n");
fprintf(lanfp, " This document is used for tests with HTTP,\n");
.....
fprintf(lanfp, "HTTP/1.0 404 Not Found\r\n"); /* Status line, first in the header (entity header) */
fprintf(lanfp, "Content-type: text/html\r\n"); /* Type of data in enclosed text (entity body) */
fprintf(lanfp, "Content-length: 82\r\n"); /* Size of the enclosed text (entity body) */
fprintf(lanfp, "\r\n"); /* Empty line which finishes the header (entity header) */
fprintf(lanfp, "<HTML>\n"); /* First line in the enclosed text (entity body) */
fprintf(lanfp, " <HEAD>\n");
fprintf(lanfp, " <TITLE>404 Not Found</TITLE>\n");
fprintf(lanfp, " </HEAD>\n");
fprintf(lanfp, " <BODY>\n");
fprintf(lanfp, " <H1>404 Not Found</H1>\n\n");
fprintf(lanfp, " HTTP/1.0 404 Not Found\n");
.....
fprintf(lanfp, "GET /cgi-bin/pushtest HTTP/1.0\r\n"); /* Request line, first in the header (entity header) */
fprintf(lanfp, "\r\n");
fprintf(lanfp, "HTTP/1.0 200 OK\r\n"); /* Status line, first in the header (entity header) */
fprintf(lanfp, "Content-type: multipart/x-mixed-replace;boundary=HSRandomString\r\n"); /* Replace type follows as of data in enclosed file (entity body) */
fprintf(lanfp, "\r\n"); /* Empty line which finishes the header (entity header) */
fprintf(lanfp, "--HSRandomString\r\n"); /* Marks the beginning of the first replace block */
fprintf(lanfp, "Content-type: text/html\r\n"); /* Type of data in enclosed replace block */
fprintf(lanfp, "\r\n"); /* Empty line which finishes the replace block header */
fprintf(lanfp, "<H1>Test of HTTP for server push</H1>\n\n"); /* First line of the replace block (i.e. entity body) */
fprintf(lanfp, "Test block number 1\n");
fprintf(lanfp, "--HSRandomString\r\n"); /* Marks the beginning of the second replace block */
fprintf(lanfp, "Content-type: text/html\r\n"); /* Type of data in enclosed replace block */
fprintf(lanfp, "\r\n"); /* Empty line which finishes the replace block header */
fprintf(lanfp, "<H1>Test of HTTP for server push</H1>\n\n"); /* First line of the replace block (i.e. entity body) */
fprintf(lanfp, "Test block number 2\n");
.....
"webmaster" for the domain "karnak" in Sweden ("se")