1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2000-2018, University of Amsterdam 7 VU University Amsterdam 8 CWI, Amsterdam 9 All rights reserved. 10 11 Redistribution and use in source and binary forms, with or without 12 modification, are permitted provided that the following conditions 13 are met: 14 15 1. Redistributions of source code must retain the above copyright 16 notice, this list of conditions and the following disclaimer. 17 18 2. Redistributions in binary form must reproduce the above copyright 19 notice, this list of conditions and the following disclaimer in 20 the documentation and/or other materials provided with the 21 distribution. 22 23 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 24 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 25 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 26 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 27 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 28 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 29 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 30 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 31 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 33 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 34 POSSIBILITY OF SUCH DAMAGE. 35*/ 36 37:- module(socket, 38 [ tcp_socket/1, % -Socket 39 tcp_close_socket/1, % +Socket 40 tcp_open_socket/3, % +Socket, -Read, -Write 41 tcp_connect/2, % +Socket, +Address 42 tcp_connect/3, % +Socket, +Address, -StreamPair 43 tcp_connect/4, % +Socket, +Address, -Read, -Write) 44 tcp_bind/2, % +Socket, +Address 45 tcp_accept/3, % +Master, -Slave, -PeerName 46 tcp_listen/2, % +Socket, +BackLog 47 tcp_fcntl/3, % +Socket, +Command, ?Arg 48 tcp_setopt/2, % +Socket, +Option 49 tcp_getopt/2, % +Socket, ?Option 50 tcp_host_to_address/2, % ?HostName, ?Ip-nr 51 tcp_select/3, % +Inputs, -Ready, +Timeout 52 gethostname/1, % -HostName 53 54 tcp_open_socket/2, % +Socket, -StreamPair 55 56 udp_socket/1, % -Socket 57 udp_receive/4, % +Socket, -Data, -Sender, +Options 58 udp_send/4, % +Socket, +Data, +Sender, +Options 59 60 negotiate_socks_connection/2% +DesiredEndpoint, +StreamPair 61 ]). 62:- use_module(library(shlib)). 63:- use_module(library(debug)). 64:- use_module(library(lists)). 65 66/** <module> Network socket (TCP and UDP) library 67 68The library(socket) provides TCP and UDP inet-domain sockets from 69SWI-Prolog, both client and server-side communication. The interface of 70this library is very close to the Unix socket interface, also supported 71by the MS-Windows _winsock_ API. SWI-Prolog applications that wish to 72communicate with multiple sources have three options: 73 74 - Use I/O multiplexing based on wait_for_input/3. On Windows 75 systems this can only be used for sockets, not for general 76 (device-) file handles. 77 - Use multiple threads, handling either a single blocking socket 78 or a pool using I/O multiplexing as above. 79 - Using XPCE's class `socket` which synchronises socket 80 events in the GUI event-loop. 81 82## Client applications {#socket-server} 83 84Using this library to establish a TCP connection to a server is as 85simple as opening a file. See also http_open/3. 86 87== 88dump_swi_homepage :- 89 setup_call_cleanup( 90 tcp_connect(www.swi-prolog.org:http, Stream, []), 91 ( format(Stream, 92 'GET / HTTP/1.1~n\c 93 Host: www.swi-prolog.org~n\c 94 Connection: close~n~n', []), 95 flush_output(Stream), 96 copy_stream_data(Stream, current_output) 97 ), 98 close(S)). 99== 100 101To deal with timeouts and multiple connections, threads, 102wait_for_input/3 and/or non-blocking streams (see tcp_fcntl/3) can be 103used. 104 105## Server applications {#socket-client} 106 107The typical sequence for generating a server application is given below. 108To close the server, use close/1 on `AcceptFd`. 109 110 == 111 create_server(Port) :- 112 tcp_socket(Socket), 113 tcp_bind(Socket, Port), 114 tcp_listen(Socket, 5), 115 tcp_open_socket(Socket, AcceptFd, _), 116 <dispatch> 117 == 118 119There are various options for <dispatch>. The most commonly used option 120is to start a Prolog thread to handle the connection. Alternatively, 121input from multiple clients can be handled in a single thread by 122listening to these clients using wait_for_input/3. Finally, on Unix 123systems, we can use fork/1 to handle the connection in a new process. 124Note that fork/1 and threads do not cooperate well. Combinations can be 125realised but require good understanding of POSIX thread and 126fork-semantics. 127 128Below is the typical example using a thread. Note the use of 129setup_call_cleanup/3 to guarantee that all resources are reclaimed, also 130in case of failure or exceptions. 131 132 == 133 dispatch(AcceptFd) :- 134 tcp_accept(AcceptFd, Socket, _Peer), 135 thread_create(process_client(Socket, Peer), _, 136 [ detached(true) 137 ]), 138 dispatch(AcceptFd). 139 140 process_client(Socket, Peer) :- 141 setup_call_cleanup( 142 tcp_open_socket(Socket, StreamPair), 143 handle_service(In, StreamPair), 144 close(StreamPair)). 145 146 handle_service(StreamPair) :- 147 ... 148 == 149 150## Socket exceptions {#socket-exceptions} 151 152Errors that are trapped by the low-level library are mapped to an 153exception of the shape below. In this term, `Code` is a lower case atom 154that corresponds to the C macro name, e.g., `epipe` for a broken pipe. 155`Message` is the human readable string for the error code returned by 156the OS or the same as `Code` if the OS does not provide this 157functionality. Note that `Code` is derived from a static set of macros 158that may or may not be defines for the target OS. If the macro name is 159not known, `Code` is =|ERROR_nnn|=, where _nnn_ is an integer. 160 161 error(socket_error(Code, Message), _) 162 163Note that on Windows `Code` is a ``wsa*`` code which makes it hard to 164write portable code that handles specific socket errors. Even on POSIX 165systems the exact set of errors produced by the network stack is not 166defined. 167 168## TCP socket predicates {#socket-predicates} 169*/ 170 171:- multifile 172 tcp_connect_hook/3, % +Socket, +Addr, -In, -Out 173 tcp_connect_hook/4, % +Socket, +Addr, -Stream 174 proxy_for_url/3, % +URL, +Host, -ProxyList 175 try_proxy/4. % +Proxy, +Addr, -Socket, -Stream 176 177:- predicate_options(tcp_connect/3, 3, 178 [ bypass_proxy(boolean), 179 nodelay(boolean) 180 ]). 181 182:- use_foreign_library(foreign(socket), install_socket). 183:- public tcp_debug/1. % set debugging. 184 185%! tcp_socket(-SocketId) is det. 186% 187% Creates an INET-domain stream-socket and unifies an identifier 188% to it with SocketId. On MS-Windows, if the socket library is not 189% yet initialised, this will also initialise the library. 190 191%! tcp_close_socket(+SocketId) is det. 192% 193% Closes the indicated socket, making SocketId invalid. Normally, 194% sockets are closed by closing both stream handles returned by 195% open_socket/3. There are two cases where tcp_close_socket/1 is 196% used because there are no stream-handles: 197% 198% - If, after tcp_accept/3, the server uses fork/1 to handle the 199% client in a sub-process. In this case the accepted socket is 200% not longer needed from the main server and must be discarded 201% using tcp_close_socket/1. 202% - If, after discovering the connecting client with 203% tcp_accept/3, the server does not want to accept the 204% connection, it should discard the accepted socket 205% immediately using tcp_close_socket/1. 206 207%! tcp_open_socket(+SocketId, -StreamPair) is det. 208% 209% Create streams to communicate to SocketId. If SocketId is a 210% master socket (see tcp_bind/2), StreamPair should be used for 211% tcp_accept/3. If SocketId is a connected (see tcp_connect/2) or 212% accepted socket (see tcp_accept/3), StreamPair is unified to a 213% stream pair (see stream_pair/3) that can be used for reading and 214% writing. The stream or pair must be closed with close/1, which 215% also closes SocketId. 216 217tcp_open_socket(Socket, Stream) :- 218 tcp_open_socket(Socket, In, Out), 219 ( var(Out) 220 -> Stream = In 221 ; stream_pair(Stream, In, Out) 222 ). 223 224%! tcp_open_socket(+SocketId, -InStream, -OutStream) is det. 225% 226% Similar to tcp_open_socket/2, but creates two separate sockets 227% where tcp_open_socket/2 would have created a stream pair. 228% 229% @deprecated New code should use tcp_open_socket/2 because 230% closing a stream pair is much easier to perform safely. 231 232%! tcp_bind(SocketId, ?Address) is det. 233% 234% Bind the socket to Address on the current machine. This 235% operation, together with tcp_listen/2 and tcp_accept/3 implement 236% the _server-side_ of the socket interface. Address is either an 237% plain `Port` or a term HostPort. The first form binds the socket 238% to the given port on all interfaces, while the second only binds 239% to the matching interface. A typical example is below, causing 240% the socket to listen only on port 8080 on the local machine's 241% network. 242% 243% == 244% tcp_bind(Socket, localhost:8080) 245% == 246% 247% If `Port` is unbound, the system picks an arbitrary free port 248% and unifies `Port` with the selected port number. `Port` is 249% either an integer or the name of a registered service. See also 250% tcp_connect/4. 251 252%! tcp_listen(+SocketId, +BackLog) is det. 253% 254% Tells, after tcp_bind/2, the socket to listen for incoming 255% requests for connections. Backlog indicates how many pending 256% connection requests are allowed. Pending requests are requests 257% that are not yet acknowledged using tcp_accept/3. If the 258% indicated number is exceeded, the requesting client will be 259% signalled that the service is currently not available. A 260% commonly used default value for Backlog is 5. 261 262%! tcp_accept(+Socket, -Slave, -Peer) is det. 263% 264% This predicate waits on a server socket for a connection request 265% by a client. On success, it creates a new socket for the client 266% and binds the identifier to Slave. Peer is bound to the 267% IP-address of the client. 268 269%! tcp_connect(+SocketId, +HostAndPort) is det. 270% 271% Connect SocketId. After successful completion, tcp_open_socket/3 272% can be used to create I/O-Streams to the remote socket. This 273% predicate is part of the low level client API. A connection to a 274% particular host and port is realised using these steps: 275% 276% == 277% tcp_socket(Socket), 278% tcp_connect(Socket, Host:Port), 279% tcp_open_socket(Socket, StreamPair) 280% == 281% 282% Typical client applications should use the high level interface 283% provided by tcp_connect/3 which avoids resource leaking if a 284% step in the process fails, and can be hooked to support proxies. 285% For example: 286% 287% == 288% setup_call_cleanup( 289% tcp_connect(Host:Port, StreamPair, []), 290% talk(StreamPair), 291% close(StreamPair)) 292% == 293 294 295 /******************************* 296 * HOOKABLE CONNECT * 297 *******************************/ 298 299%! tcp_connect(+Socket, +Address, -Read, -Write) is det. 300% 301% Connect a (client) socket to Address and return a bi-directional 302% connection through the stream-handles Read and Write. This 303% predicate may be hooked by defining socket:tcp_connect_hook/4 304% with the same signature. Hooking can be used to deal with proxy 305% connections. E.g., 306% 307% == 308% :- multifile socket:tcp_connect_hook/4. 309% 310% socket:tcp_connect_hook(Socket, Address, Read, Write) :- 311% proxy(ProxyAdress), 312% tcp_connect(Socket, ProxyAdress), 313% tcp_open_socket(Socket, Read, Write), 314% proxy_connect(Address, Read, Write). 315% == 316% 317% @deprecated New code should use tcp_connect/3 called as 318% tcp_connect(+Address, -StreamPair, +Options). 319 320tcp_connect(Socket, Address, Read, Write) :- 321 tcp_connect_hook(Socket, Address, Read, Write), 322 !. 323tcp_connect(Socket, Address, Read, Write) :- 324 tcp_connect(Socket, Address), 325 tcp_open_socket(Socket, Read, Write). 326 327 328 329%! tcp_connect(+Address, -StreamPair, +Options) is det. 330%! tcp_connect(+Socket, +Address, -StreamPair) is det. 331% 332% Establish a TCP communication as a client. The +,-,+ mode is the 333% preferred way for a client to establish a connection. This 334% predicate can be hooked to support network proxies. To use a 335% proxy, the hook proxy_for_url/3 must be defined. Permitted 336% options are: 337% 338% * bypass_proxy(+Boolean) 339% Defaults to =false=. If =true=, do not attempt to use any 340% proxies to obtain the connection 341% 342% * nodelay(+Boolean) 343% Defaults to =false=. If =true=, set nodelay on the 344% resulting socket using tcp_setopt(Socket, nodelay) 345% 346% The +,+,- mode is deprecated and does not support proxies. It 347% behaves like tcp_connect/4, but creates a stream pair (see 348% stream_pair/3). 349% 350% @error proxy_error(tried(ResultList)) is raised by mode (+,-,+) 351% if proxies are defines by proxy_for_url/3 but no proxy can 352% establsh the connection. `ResultList` contains one or more terms 353% of the form false(Proxy) for a hook that simply failed or 354% error(Proxy, ErrorTerm) for a hook that raised an exception. 355% 356% @see library(http/http_proxy) defines a hook that allows to 357% connect through HTTP proxies that support the =CONNECT= method. 358 359% Main mode: +,-,+ 360tcp_connect(Address, StreamPair, Options) :- 361 var(StreamPair), 362 !, 363 ( memberchk(bypass_proxy(true), Options) 364 -> tcp_connect_direct(Address, Socket, StreamPair) 365 ; findall(Result, 366 try_a_proxy(Address, Result), 367 ResultList), 368 last(ResultList, Status) 369 -> ( Status = true(_Proxy, Socket, StreamPair) 370 -> true 371 ; throw(error(proxy_error(tried(ResultList)), _)) 372 ) 373 ; tcp_connect_direct(Address, Socket, StreamPair) 374 ), 375 ( memberchk(nodelay(true), Options) 376 -> tcp_setopt(Socket, nodelay) 377 ; true 378 ). 379% backward compatibility mode +,+,- 380tcp_connect(Socket, Address, StreamPair) :- 381 tcp_connect_hook(Socket, Address, StreamPair0), 382 !, 383 StreamPair = StreamPair0. 384tcp_connect(Socket, Address, StreamPair) :- 385 tcp_connect(Socket, Address, Read, Write), 386 stream_pair(StreamPair, Read, Write). 387 388 389tcp_connect_direct(Address, Socket, StreamPair):- 390 tcp_socket(Socket), 391 catch(tcp_connect(Socket, Address, StreamPair), 392 Error, 393 ( tcp_close_socket(Socket), 394 throw(Error) 395 )). 396 397%! tcp_select(+ListOfStreams, -ReadyList, +TimeOut) 398% 399% Same as the built-in wait_for_input/3. Used to allow for interrupts 400% and timeouts on Windows. A redesign of the Windows socket interface 401% makes it impossible to do better than Windows select() call 402% underlying wait_for_input/3. As input multiplexing typically happens 403% in a background thread anyway we accept the loss of timeouts and 404% interrupts. 405% 406% @deprecated Use wait_for_input/3 407 408tcp_select(ListOfStreams, ReadyList, TimeOut) :- 409 wait_for_input(ListOfStreams, ReadyList, TimeOut). 410 411 412 /******************************* 413 * PROXY SUPPORT * 414 *******************************/ 415 416try_a_proxy(Address, Result) :- 417 format(atom(URL), 'socket://~w', [Address]), 418 ( Address = Host:_ 419 -> true 420 ; Host = Address 421 ), 422 proxy_for_url(URL, Host, Proxy), 423 debug(socket(proxy), 'Socket connecting via ~w~n', [Proxy]), 424 ( catch(try_proxy(Proxy, Address, Socket, Stream), E, true) 425 -> ( var(E) 426 -> !, Result = true(Proxy, Socket, Stream) 427 ; Result = error(Proxy, E) 428 ) 429 ; Result = false(Proxy) 430 ), 431 debug(socket(proxy), 'Socket: ~w: ~p', [Proxy, Result]). 432 433%! try_proxy(+Proxy, +TargetAddress, -Socket, -StreamPair) is semidet. 434% 435% Attempt a socket-level connection via the given proxy to 436% TargetAddress. The Proxy argument must match the output argument 437% of proxy_for_url/3. The predicate tcp_connect/3 (and http_open/3 438% from the library(http/http_open)) collect the results of failed 439% proxies and raise an exception no proxy is capable of realizing 440% the connection. 441% 442% The default implementation recognises the values for Proxy 443% described below. The library(http/http_proxy) adds 444% proxy(Host,Port) which allows for HTTP proxies using the 445% =CONNECT= method. 446% 447% - direct 448% Do not use any proxy 449% - socks(Host, Port) 450% Use a SOCKS5 proxy 451 452:- multifile 453 try_proxy/4. 454 455try_proxy(direct, Address, Socket, StreamPair) :- 456 !, 457 tcp_connect_direct(Address, Socket, StreamPair). 458try_proxy(socks(Host, Port), Address, Socket, StreamPair) :- 459 !, 460 tcp_connect_direct(Host:Port, Socket, StreamPair), 461 catch(negotiate_socks_connection(Address, StreamPair), 462 Error, 463 ( close(StreamPair, [force(true)]), 464 throw(Error) 465 )). 466 467%! proxy_for_url(+URL, +Hostname, -Proxy) is nondet. 468% 469% This hook can be implemented to return a proxy to try when 470% connecting to URL. Returned proxies are tried in the order in 471% which they are returned by the multifile hook try_proxy/4. 472% Pre-defined proxy methods are: 473% 474% * direct 475% connect directly to the resource 476% * proxy(Host, Port) 477% Connect to the resource using an HTTP proxy. If the 478% resource is not an HTTP URL, then try to connect using the 479% CONNECT verb, otherwise, use the GET verb. 480% * socks(Host, Port) 481% Connect to the resource via a SOCKS5 proxy 482% 483% These correspond to the proxy methods defined by PAC [Proxy 484% auto-config](http://en.wikipedia.org/wiki/Proxy_auto-config). 485% Additional methods can be returned if suitable clauses for 486% http:http_connection_over_proxy/6 or try_proxy/4 are defined. 487 488:- multifile 489 proxy_for_url/3. 490 491 492 /******************************* 493 * OPTIONS * 494 *******************************/ 495 496%! tcp_setopt(+SocketId, +Option) is det. 497% 498% Set options on the socket. Defined options are: 499% 500% - reuseaddr 501% Allow servers to reuse a port without the system being 502% completely sure the port is no longer in use. 503% 504% - bindtodevice(+Device) 505% Bind the socket to Device (an atom). For example, the code 506% below binds the socket to the _loopback_ device that is 507% typically used to realise the _localhost_. See the manual 508% pages for setsockopt() and the socket interface (e.g., 509% socket(7) on Linux) for details. 510% 511% == 512% tcp_socket(Socket), 513% tcp_setopt(Socket, bindtodevice(lo)) 514% == 515% 516% - nodelay 517% - nodelay(true) 518% If =true=, disable the Nagle optimization on this socket, 519% which is enabled by default on almost all modern TCP/IP 520% stacks. The Nagle optimization joins small packages, which is 521% generally desirable, but sometimes not. Please note that the 522% underlying TCP_NODELAY setting to setsockopt() is not 523% available on all platforms and systems may require additional 524% privileges to change this option. If the option is not 525% supported, tcp_setopt/2 raises a domain_error exception. See 526% [Wikipedia](http://en.wikipedia.org/wiki/Nagle's_algorithm) 527% for details. 528% 529% - broadcast 530% UDP sockets only: broadcast the package to all addresses 531% matching the address. The address is normally the address of 532% the local subnet (i.e. 192.168.1.255). See udp_send/4. 533% 534% - ip_add_membership(+MultiCastGroup) 535% - ip_add_membership(+MultiCastGroup, +LocalInterface) 536% - ip_add_membership(+MultiCastGroup, +LocalInterface, +InterfaceIndex) 537% - ip_drop_membership(+MultiCastGroup) 538% - ip_drop_membership(+MultiCastGroup, +LocalInterface) 539% - ip_drop_membership(+MultiCastGroup, +LocalInterface, +InterfaceIndex) 540% Join/leave a multicast group. Calls setsockopt() with the 541% corresponding arguments. 542% 543% - dispatch(+Boolean) 544% In GUI environments (using XPCE or the Windows =swipl-win.exe= 545% executable) this flags defines whether or not any events are 546% dispatched on behalf of the user interface. Default is 547% =true=. Only very specific situations require setting 548% this to =false=. 549 550%! tcp_fcntl(+Stream, +Action, ?Argument) is det. 551% 552% Interface to the fcntl() call. Currently only suitable to deal 553% switch stream to non-blocking mode using: 554% 555% == 556% tcp_fcntl(Stream, setfl, nonblock), 557% == 558% 559% An attempt to read from a non-blocking stream while there is no 560% data available returns -1 (or =end_of_file= for read/1), but 561% at_end_of_stream/1 fails. On actual end-of-input, 562% at_end_of_stream/1 succeeds. 563 564tcp_fcntl(Socket, setfl, nonblock) :- 565 !, 566 tcp_setopt(Socket, nonblock). 567 568%! tcp_getopt(+Socket, ?Option) is semidet. 569% 570% Get information about Socket. Defined properties are below. 571% Requesting an unknown option results in a `domain_error` exception. 572% 573% - file_no(-File) 574% Get the OS file handle as an integer. This may be used for 575% debugging and integration. 576 577%! tcp_host_to_address(?HostName, ?Address) is det. 578% 579% Translate between a machines host-name and it's (IP-)address. If 580% HostName is an atom, it is resolved using getaddrinfo() and the 581% IP-number is unified to Address using a term of the format 582% ip(Byte1,Byte2,Byte3,Byte4). Otherwise, if Address is bound to 583% an ip(Byte1,Byte2,Byte3,Byte4) term, it is resolved by 584% gethostbyaddr() and the canonical hostname is unified with 585% HostName. 586% 587% @tbd This function should support more functionality provided by 588% gethostbyaddr, probably by adding an option-list. 589 590%! gethostname(-Hostname) is det. 591% 592% Return the canonical fully qualified name of this host. This is 593% achieved by calling gethostname() and return the canonical name 594% returned by getaddrinfo(). 595 596 597 /******************************* 598 * SOCKS * 599 *******************************/ 600 601%! negotiate_socks_connection(+DesiredEndpoint, +StreamPair) is det. 602% 603% Negotiate a connection to DesiredEndpoint over StreamPair. 604% DesiredEndpoint should be in the form of either: 605% 606% * hostname : port 607% * ip(A,B,C,D) : port 608% 609% @error socks_error(Details) if the SOCKS negotiation failed. 610 611negotiate_socks_connection(Host:Port, StreamPair):- 612 format(StreamPair, '~s', [[0x5, % Version 5 613 0x1, % 1 auth method supported 614 0x0]]), % which is 'no auth' 615 flush_output(StreamPair), 616 get_byte(StreamPair, ServerVersion), 617 get_byte(StreamPair, AuthenticationMethod), 618 ( ServerVersion =\= 0x05 619 -> throw(error(socks_error(invalid_version(5, ServerVersion)), _)) 620 ; AuthenticationMethod =:= 0xff 621 -> throw(error(socks_error(invalid_authentication_method( 622 0xff, 623 AuthenticationMethod)), _)) 624 ; true 625 ), 626 ( Host = ip(A,B,C,D) 627 -> AddressType = 0x1, % IPv4 Address 628 format(atom(Address), '~s', [[A, B, C, D]]) 629 ; AddressType = 0x3, % Domain 630 atom_length(Host, Length), 631 format(atom(Address), '~s~w', [[Length], Host]) 632 ), 633 P1 is Port /\ 0xff, 634 P2 is Port >> 8, 635 format(StreamPair, '~s~w~s', [[0x5, % Version 5 636 0x1, % Please establish a connection 637 0x0, % reserved 638 AddressType], 639 Address, 640 [P2, P1]]), 641 flush_output(StreamPair), 642 get_byte(StreamPair, _EchoedServerVersion), 643 get_byte(StreamPair, Status), 644 ( Status =:= 0 % Established! 645 -> get_byte(StreamPair, _Reserved), 646 get_byte(StreamPair, EchoedAddressType), 647 ( EchoedAddressType =:= 0x1 648 -> get_byte(StreamPair, _), % read IP4 649 get_byte(StreamPair, _), 650 get_byte(StreamPair, _), 651 get_byte(StreamPair, _) 652 ; get_byte(StreamPair, Length), % read host name 653 forall(between(1, Length, _), 654 get_byte(StreamPair, _)) 655 ), 656 get_byte(StreamPair, _), % read port 657 get_byte(StreamPair, _) 658 ; throw(error(socks_error(negotiation_rejected(Status)), _)) 659 ). 660 661 662 /******************************* 663 * MESSAGES * 664 *******************************/ 665 666/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 667The C-layer generates exceptions of the following format, where Message 668is extracted from the operating system. 669 670 error(socket_error(Code, Message), _) 671- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 672 673:- multifile 674 prolog:error_message//1. 675 676prologerror_message(socket_error(_Code, Message)) --> 677 [ 'Socket error: ~w'-[Message] ]. 678prologerror_message(socks_error(Error)) --> 679 socks_error(Error). 680prologerror_message(proxy_error(tried(Tried))) --> 681 [ 'Failed to connect using a proxy. Tried:'-[], nl], 682 proxy_tried(Tried). 683 684socks_error(invalid_version(Supported, Got)) --> 685 [ 'SOCKS: unsupported version: ~p (supported: ~p)'- 686 [ Got, Supported ] ]. 687socks_error(invalid_authentication_method(Supported, Got)) --> 688 [ 'SOCKS: unsupported authentication method: ~p (supported: ~p)'- 689 [ Got, Supported ] ]. 690socks_error(negotiation_rejected(Status)) --> 691 [ 'SOCKS: connection failed: ~p'-[Status] ]. 692 693proxy_tried([]) --> []. 694proxy_tried([H|T]) --> 695 proxy_tried(H), 696 proxy_tried(T). 697proxy_tried(error(Proxy, Error)) --> 698 [ '~w: '-[Proxy] ], 699 '$messages':translate_message(Error). 700proxy_tried(false(Proxy)) --> 701 [ '~w: failed with unspecified error'-[Proxy] ]