% ---------------------------------------------------------------------- % System: ECLiPSe Constraint Logic Programming System % Copyright (C) Imperial College London and ICL 1995-1999 % Version: $Id: http_server.pl,v 1.6 2004/10/27 14:32:37 ajs2 Exp $ % ---------------------------------------------------------------------- /* RPC using HTTP/1.0 (request status line) and MIME-Version:1.0 (request general header) SERVER http document used is HTTP/1.0 from the Network Working Group - internet draft - expiring in june, 19 1995. */ :- module(http_server). :- comment(summary, "HTTP server library"). :- comment(author, "Ph. Bonnet, S. Bressan and M. Meier, ECRC Munich"). :- comment(copyright, "Imperial College London and ICL"). :- comment(date, "$Date: 2004/10/27 14:32:37 $"). :- export http_server/1, http_server/2. :- use_module(http_grammar). /* http_server(+Port) - creation of a socket, bind it to current Host and Port and listen - loop */ http_server(Port):- http_server(Port, 1). http_server(Port, Pending):- setval(port, Port), socket(internet, stream, Soc), bind(Soc, _/Port), listen(Soc, Pending), loop(Soc). /* loop: - accept a connection on the socket - reception of a request - decoding of the request (method + url + http param init) - call of the server function - encoding of the response (depending on server function) - send the response on the socket */ loop(Soc):- accept(Soc, _, S), (block(process(S), _Tag, true) -> true ; true ), close(S),!, loop(Soc). loop(Soc):- loop(Soc). process(S):- request_recp(S, Method, URL, ReqHttpParams, ObjectBody), call(http_method(Method, URL, ObjectBody, Output, Status, RespHttpParams), http_method), analyse_para(ReqHttpParams, RespHttpParams, HttpParams), respons_enco(Output, Status, HttpParams, Response), respons_send(S, Response). /* The request reception reads from the socket stream a full request sent by the client. Only http full requests are recognised (http document p. 15). The request is returned as the Method, the URL and a set of parameters defined in the header, plus the object body The header is constituted of lindes separated by \r \n. The header is separated from the object body by a \r \n. The length of the object body is a parameter in the header */ request_recp(S, Method, Url, HttpParams, ObjectBody):- read_parse_Header(S, Method, Url, HttpParams), (member(contentLength(BL), HttpParams) -> read_Object(S, BL, ObjectBody) ; true ). read_parse_Header(Stream, Method, Url, HttpParams):- read_SL(Stream, SL), parse_SL(SL, Method, Url), read_Params(Stream, Params), parse_Params(Params, HttpParams). /* status line */ read_SL(S, Line):- read_string(S, "\r\n", _, Line), read_string(S, "\r\n", L, _), L==0. parse_SL(Line, Method, Url):- open(Line, string, s), read_string(s, " ", _, Method), read_string(s, " ", _, Url), close(s). /* general header* request header* object header* */ read_Params(S, List):- read_Params(S, [], List). read_Params(S, L0, L):- read_string(S, "\r\n", Length, Elem), Length \== 0, !, read_string(S, "\r\n", LLength, _), LLength == 0, append(L0, [Elem], L1), read_Params(S, L1, L). read_Params(S, L, L):- read_string(S, "\r\n", Length, _), Length == 0. /* parsing using the DCG grammar */ parse_Params([], []). parse_Params([H|T], [P|TT]):- append_strings(H, "\n", HH), open(HH, string, s), token_to_list(s, L), close(s), phrase(header(P), L, _), !, parse_Params(T, TT). /* read the object according to the object length that is contained in the header. */ read_Object(S, BL, ObjectBody):- read_string(S, "", BL, ObjectBody). /* analyse of the Url */ analyse_Url(Url, Path):- open(Url, string, s), read_string(s, "//", _, _), read_string(s, "/", _, _), read_string(s, "", Path, _), close(s). /* rpc call: executes the method on the object and return: - the output of the method (possibly empty) - a status code for the response status line - a list of http parameters (in particular the length of the object body). http_rpcInterface(Method, Url, ObjectBody, Output, 200, [contentLength(CL)]):- concat_string(["Vous avez demande la methode ", Method, "sur l'objet ", Url], Output), string_length(Output, CL). */ /* http paramter analysis: compatibility between response and request parameters. constitution of the list of parameters for the response */ analyse_para(_, HttpParams, HttpParams). /* response encoding: - response status - response header - object body */ respons_enco(Output, Status, HttpParams, Response):- resp_SL(Status, SL), resp_Header(HttpParams, Header), concat_string([SL, Header, "\n" ], H), concat_strings(H, Output, Response). resp_SL(Status, SL):- integer_atom(Status, S), atom_string(S, SC), substring(SC, 1, 1, RP), concat_string(["HTTP/1.0 ", SC, " ", RP, "\n"], SL). resp_Header(HttpParams, Header):- resp_Header(HttpParams, "", Header). resp_Header([], S, S). resp_Header([H|T], S0, S):- phrase(header(H), L, _), open(_, string, s), list_to_token(L, s), current_stream(S1, string, s), close(s), concat_string([S0, S1, "\n"], S2), resp_Header(T, S2, S). /* response sending */ respons_send(Stream, String):- open(String, string, StreamString), sub_respons_send(Stream, StreamString), close(StreamString). sub_respons_send(Stream, StreamString):- read_string(StreamString, "", 250, String),!, write(Stream, String), flush(Stream), sub_respons_send(Stream, StreamString). sub_respons_send(_, _). %---------------------------------------------------------------------- :- comment(http_server/1, [ template:"http_server(+Port)", summary:"Start an http server", args:["Method":"An integer port number"], desc:html(" The server does: NOTE: The predicate http_server/1 requires that a module http_method is defined that contains a predicate http_method/6. This predicate is used by the programmer to customize the server. For instance the method GET can be simply implemented. The programmer can define its own methods.

A simple example of server is the implementation of the method GET. A module is created that contains the predicate http_method/6 that implements the method GET: a read on the file identified by its URL. The file is returned if it is found, otherwise an error parameter is returned.

This simple program can be used to test HTML pages. Viewers such as Netscape provide a view code option that signalizes syntax errors in the HTML code. This simple program can be used as a light weight testing tool, possibly launched from the directory where the HTML page resides. "), eg:" [eclipse 1]: [user]. /******************************************************************** * test (server) *******************************************************************/ :- module(http_method). :- set_error_handler(170, fail/0). :- set_error_handler(171, fail/0). /* http_method(+Method, +Url, +ObjectBody, -Output, -StatusCode, -Parameter) executes the method on the object and returns: - the output of the method (possibly empty) - a status code for the response status line - a list of http parameters (in particular the length of the object body). */ http_method(\"GET\", Url, _, Contents, 200, [contentLength(CL)]):- append_strings(\"/\", FileName, Url), getContents(FileName, Contents), !, string_length(Contents, CL). http_method(\"GET\", _, _, \"\", 404, []). getContents(Url, Contents):- open(Url, read, s), read_string(s, \"\", _, Contents), close(s). ^D yes. [eclipse 2]: use_module(http). http_grammar.pl compiled traceable 25048 bytes in 0.27 seconds http_client.pl compiled traceable 6052 bytes in 0.28 seconds http_server.pl compiled traceable 5564 bytes in 0.03 seconds http.pl compiled traceable 0 bytes in 0.35 seconds yes. [eclipse 3]: use_module(http_method). yes. [eclipse 4]: http_server(8000). "]). :- comment(http_server/2, [ template:"http_server(+Port,+Pending)", summary:"Start an http server with allows the specified number of pending connections", args:["Method":"An integer port number", "Pending":"The number of simultaneous connections to queue up before rejecting"], desc:html("http_server/1 corresponds to a pending queue size of 1.")]).