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) 2000-2020, 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:- autoload(library(debug),[debug/3]). 63:- autoload(library(lists),[last/2]). 64 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(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:- if(current_predicate(unix_domain_socket/1)). 186:- export(unix_domain_socket/1). % -Socket 187:- endif. 188 189%! tcp_socket(-SocketId) is det. 190% 191% Creates an INET-domain stream-socket and unifies an identifier 192% to it with SocketId. On MS-Windows, if the socket library is not 193% yet initialised, this will also initialise the library. 194 195%! tcp_close_socket(+SocketId) is det. 196% 197% Closes the indicated socket, making SocketId invalid. Normally, 198% sockets are closed by closing both stream handles returned by 199% open_socket/3. There are two cases where tcp_close_socket/1 is 200% used because there are no stream-handles: 201% 202% - If, after tcp_accept/3, the server uses fork/1 to handle the 203% client in a sub-process. In this case the accepted socket is 204% not longer needed from the main server and must be discarded 205% using tcp_close_socket/1. 206% - If, after discovering the connecting client with 207% tcp_accept/3, the server does not want to accept the 208% connection, it should discard the accepted socket 209% immediately using tcp_close_socket/1. 210 211%! tcp_open_socket(+SocketId, -StreamPair) is det. 212% 213% Create streams to communicate to SocketId. If SocketId is a 214% master socket (see tcp_bind/2), StreamPair should be used for 215% tcp_accept/3. If SocketId is a connected (see tcp_connect/2) or 216% accepted socket (see tcp_accept/3), StreamPair is unified to a 217% stream pair (see stream_pair/3) that can be used for reading and 218% writing. The stream or pair must be closed with close/1, which 219% also closes SocketId. 220 221tcp_open_socket(Socket, Stream) :- 222 tcp_open_socket(Socket, In, Out), 223 ( var(Out) 224 -> Stream = In 225 ; stream_pair(Stream, In, Out) 226 ). 227 228%! tcp_open_socket(+SocketId, -InStream, -OutStream) is det. 229% 230% Similar to tcp_open_socket/2, but creates two separate sockets 231% where tcp_open_socket/2 would have created a stream pair. 232% 233% @deprecated New code should use tcp_open_socket/2 because 234% closing a stream pair is much easier to perform safely. 235 236%! tcp_bind(SocketId, ?Address) is det. 237% 238% Bind the socket to Address on the current machine. This 239% operation, together with tcp_listen/2 and tcp_accept/3 implement 240% the _server-side_ of the socket interface. Address is either an 241% plain `Port` or a term HostPort. The first form binds the socket 242% to the given port on all interfaces, while the second only binds 243% to the matching interface. A typical example is below, causing 244% the socket to listen only on port 8080 on the local machine's 245% network. 246% 247% == 248% tcp_bind(Socket, localhost:8080) 249% == 250% 251% If `Port` is unbound, the system picks an arbitrary free port 252% and unifies `Port` with the selected port number. `Port` is 253% either an integer or the name of a registered service. See also 254% tcp_connect/4. 255 256%! tcp_listen(+SocketId, +BackLog) is det. 257% 258% Tells, after tcp_bind/2, the socket to listen for incoming 259% requests for connections. Backlog indicates how many pending 260% connection requests are allowed. Pending requests are requests 261% that are not yet acknowledged using tcp_accept/3. If the 262% indicated number is exceeded, the requesting client will be 263% signalled that the service is currently not available. A 264% commonly used default value for Backlog is 5. 265 266%! tcp_accept(+Socket, -Slave, -Peer) is det. 267% 268% This predicate waits on a server socket for a connection request by 269% a client. On success, it creates a new socket for the client and 270% binds the identifier to Slave. Peer is bound to the IP-address of 271% the client or the atom `af_unix` if Socket is an AF_UNIX socket (see 272% unix_domain_socket/1). 273 274%! tcp_connect(+SocketId, +Address) is det. 275% 276% Connect SocketId. After successful completion, tcp_open_socket/3 277% can be used to create I/O-Streams to the remote socket. This 278% predicate is part of the low level client API. A connection to a 279% particular host and port is realised using these steps: 280% 281% == 282% tcp_socket(Socket), 283% tcp_connect(Socket, Host:Port), 284% tcp_open_socket(Socket, StreamPair) 285% == 286% 287% Typical client applications should use the high level interface 288% provided by tcp_connect/3 which avoids resource leaking if a 289% step in the process fails, and can be hooked to support proxies. 290% For example: 291% 292% == 293% setup_call_cleanup( 294% tcp_connect(Host:Port, StreamPair, []), 295% talk(StreamPair), 296% close(StreamPair)) 297% == 298% 299% If SocketId is an AF_UNIX socket (see unix_domain_socket/1), Address 300% is an atom or string denoting a file name. 301 302 303 /******************************* 304 * HOOKABLE CONNECT * 305 *******************************/ 306 307%! tcp_connect(+Socket, +Address, -Read, -Write) is det. 308% 309% Connect a (client) socket to Address and return a bi-directional 310% connection through the stream-handles Read and Write. This 311% predicate may be hooked by defining socket:tcp_connect_hook/4 312% with the same signature. Hooking can be used to deal with proxy 313% connections. E.g., 314% 315% == 316% :- multifile socket:tcp_connect_hook/4. 317% 318% socket:tcp_connect_hook(Socket, Address, Read, Write) :- 319% proxy(ProxyAdress), 320% tcp_connect(Socket, ProxyAdress), 321% tcp_open_socket(Socket, Read, Write), 322% proxy_connect(Address, Read, Write). 323% == 324% 325% @deprecated New code should use tcp_connect/3 called as 326% tcp_connect(+Address, -StreamPair, +Options). 327 328tcp_connect(Socket, Address, Read, Write) :- 329 tcp_connect_hook(Socket, Address, Read, Write), 330 !. 331tcp_connect(Socket, Address, Read, Write) :- 332 tcp_connect(Socket, Address), 333 tcp_open_socket(Socket, Read, Write). 334 335 336 337%! tcp_connect(+Address, -StreamPair, +Options) is det. 338%! tcp_connect(+Socket, +Address, -StreamPair) is det. 339% 340% Establish a TCP communication as a client. The +,-,+ mode is the 341% preferred way for a client to establish a connection. This predicate 342% can be hooked to support network proxies. To use a proxy, the hook 343% proxy_for_url/3 must be defined. Permitted options are: 344% 345% * bypass_proxy(+Boolean) 346% Defaults to =false=. If =true=, do not attempt to use any 347% proxies to obtain the connection 348% 349% * nodelay(+Boolean) 350% Defaults to =false=. If =true=, set nodelay on the 351% resulting socket using tcp_setopt(Socket, nodelay) 352% 353% The +,+,- mode is deprecated and does not support proxies. It 354% behaves like tcp_connect/4, but creates a stream pair (see 355% stream_pair/3). 356% 357% @arg Address is either a Host:Port term or a file name (atom or 358% string). The latter connects to an AF_UNIX socket and requires 359% unix_domain_socket/1. 360% 361% @error proxy_error(tried(ResultList)) is raised by mode (+,-,+) if 362% proxies are defines by proxy_for_url/3 but no proxy can establsh the 363% connection. `ResultList` contains one or more terms of the form 364% false(Proxy) for a hook that simply failed or error(Proxy, 365% ErrorTerm) for a hook that raised an exception. 366% 367% @see library(http/http_proxy) defines a hook that allows to connect 368% through HTTP proxies that support the =CONNECT= method. 369 370% Main mode: +,-,+ 371tcp_connect(Address, StreamPair, Options) :- 372 var(StreamPair), 373 !, 374 ( memberchk(bypass_proxy(true), Options) 375 -> tcp_connect_direct(Address, Socket, StreamPair) 376 ; findall(Result, 377 try_a_proxy(Address, Result), 378 ResultList), 379 last(ResultList, Status) 380 -> ( Status = true(_Proxy, Socket, StreamPair) 381 -> true 382 ; throw(error(proxy_error(tried(ResultList)), _)) 383 ) 384 ; tcp_connect_direct(Address, Socket, StreamPair) 385 ), 386 ( memberchk(nodelay(true), Options) 387 -> tcp_setopt(Socket, nodelay) 388 ; true 389 ). 390% backward compatibility mode +,+,- 391tcp_connect(Socket, Address, StreamPair) :- 392 tcp_connect_hook(Socket, Address, StreamPair0), 393 !, 394 StreamPair = StreamPair0. 395tcp_connect(Socket, Address, StreamPair) :- 396 tcp_connect(Socket, Address, Read, Write), 397 stream_pair(StreamPair, Read, Write). 398 399 400tcp_connect_direct(Address, Socket, StreamPair):- 401 make_socket(Address, Socket), 402 catch(tcp_connect(Socket, Address, StreamPair), 403 Error, 404 ( tcp_close_socket(Socket), 405 throw(Error) 406 )). 407 408:- if(current_predicate(unix_domain_socket/1)). 409make_socket(Address, Socket) :- 410 ( atom(Address) 411 ; string(Address) 412 ), 413 !, 414 unix_domain_socket(Socket). 415:- endif. 416make_socket(_Address, Socket) :- 417 tcp_socket(Socket). 418 419 420%! tcp_select(+ListOfStreams, -ReadyList, +TimeOut) 421% 422% Same as the built-in wait_for_input/3. Used to allow for interrupts 423% and timeouts on Windows. A redesign of the Windows socket interface 424% makes it impossible to do better than Windows select() call 425% underlying wait_for_input/3. As input multiplexing typically happens 426% in a background thread anyway we accept the loss of timeouts and 427% interrupts. 428% 429% @deprecated Use wait_for_input/3 430 431tcp_select(ListOfStreams, ReadyList, TimeOut) :- 432 wait_for_input(ListOfStreams, ReadyList, TimeOut). 433 434 435 /******************************* 436 * PROXY SUPPORT * 437 *******************************/ 438 439try_a_proxy(Address, Result) :- 440 format(atom(URL), 'socket://~w', [Address]), 441 ( Address = Host:_ 442 -> true 443 ; Host = Address 444 ), 445 proxy_for_url(URL, Host, Proxy), 446 debug(socket(proxy), 'Socket connecting via ~w~n', [Proxy]), 447 ( catch(try_proxy(Proxy, Address, Socket, Stream), E, true) 448 -> ( var(E) 449 -> !, Result = true(Proxy, Socket, Stream) 450 ; Result = error(Proxy, E) 451 ) 452 ; Result = false(Proxy) 453 ), 454 debug(socket(proxy), 'Socket: ~w: ~p', [Proxy, Result]). 455 456%! try_proxy(+Proxy, +TargetAddress, -Socket, -StreamPair) is semidet. 457% 458% Attempt a socket-level connection via the given proxy to 459% TargetAddress. The Proxy argument must match the output argument 460% of proxy_for_url/3. The predicate tcp_connect/3 (and http_open/3 461% from the library(http/http_open)) collect the results of failed 462% proxies and raise an exception no proxy is capable of realizing 463% the connection. 464% 465% The default implementation recognises the values for Proxy 466% described below. The library(http/http_proxy) adds 467% proxy(Host,Port) which allows for HTTP proxies using the 468% =CONNECT= method. 469% 470% - direct 471% Do not use any proxy 472% - socks(Host, Port) 473% Use a SOCKS5 proxy 474 475:- multifile 476 try_proxy/4. 477 478try_proxy(direct, Address, Socket, StreamPair) :- 479 !, 480 tcp_connect_direct(Address, Socket, StreamPair). 481try_proxy(socks(Host, Port), Address, Socket, StreamPair) :- 482 !, 483 tcp_connect_direct(Host:Port, Socket, StreamPair), 484 catch(negotiate_socks_connection(Address, StreamPair), 485 Error, 486 ( close(StreamPair, [force(true)]), 487 throw(Error) 488 )). 489 490%! proxy_for_url(+URL, +Hostname, -Proxy) is nondet. 491% 492% This hook can be implemented to return a proxy to try when 493% connecting to URL. Returned proxies are tried in the order in 494% which they are returned by the multifile hook try_proxy/4. 495% Pre-defined proxy methods are: 496% 497% * direct 498% connect directly to the resource 499% * proxy(Host, Port) 500% Connect to the resource using an HTTP proxy. If the 501% resource is not an HTTP URL, then try to connect using the 502% CONNECT verb, otherwise, use the GET verb. 503% * socks(Host, Port) 504% Connect to the resource via a SOCKS5 proxy 505% 506% These correspond to the proxy methods defined by PAC [Proxy 507% auto-config](http://en.wikipedia.org/wiki/Proxy_auto-config). 508% Additional methods can be returned if suitable clauses for 509% http:http_connection_over_proxy/6 or try_proxy/4 are defined. 510 511:- multifile 512 proxy_for_url/3. 513 514 515 /******************************* 516 * OPTIONS * 517 *******************************/ 518 519%! tcp_setopt(+SocketId, +Option) is det. 520% 521% Set options on the socket. Defined options are: 522% 523% - reuseaddr 524% Allow servers to reuse a port without the system being 525% completely sure the port is no longer in use. 526% 527% - bindtodevice(+Device) 528% Bind the socket to Device (an atom). For example, the code 529% below binds the socket to the _loopback_ device that is 530% typically used to realise the _localhost_. See the manual 531% pages for setsockopt() and the socket interface (e.g., 532% socket(7) on Linux) for details. 533% 534% == 535% tcp_socket(Socket), 536% tcp_setopt(Socket, bindtodevice(lo)) 537% == 538% 539% - nodelay 540% - nodelay(true) 541% If =true=, disable the Nagle optimization on this socket, 542% which is enabled by default on almost all modern TCP/IP 543% stacks. The Nagle optimization joins small packages, which is 544% generally desirable, but sometimes not. Please note that the 545% underlying TCP_NODELAY setting to setsockopt() is not 546% available on all platforms and systems may require additional 547% privileges to change this option. If the option is not 548% supported, tcp_setopt/2 raises a domain_error exception. See 549% [Wikipedia](http://en.wikipedia.org/wiki/Nagle's_algorithm) 550% for details. 551% 552% - broadcast 553% UDP sockets only: broadcast the package to all addresses 554% matching the address. The address is normally the address of 555% the local subnet (i.e. 192.168.1.255). See udp_send/4. 556% 557% - ip_add_membership(+MultiCastGroup) 558% - ip_add_membership(+MultiCastGroup, +LocalInterface) 559% - ip_add_membership(+MultiCastGroup, +LocalInterface, +InterfaceIndex) 560% - ip_drop_membership(+MultiCastGroup) 561% - ip_drop_membership(+MultiCastGroup, +LocalInterface) 562% - ip_drop_membership(+MultiCastGroup, +LocalInterface, +InterfaceIndex) 563% Join/leave a multicast group. Calls setsockopt() with the 564% corresponding arguments. 565% 566% - dispatch(+Boolean) 567% In GUI environments (using XPCE or the Windows =swipl-win.exe= 568% executable) this flags defines whether or not any events are 569% dispatched on behalf of the user interface. Default is 570% =true=. Only very specific situations require setting 571% this to =false=. 572% 573% - sndbuf(+Integer) 574% Sets the send buffer size to Integer (bytes). On Windows this defaults 575% (now) to 64kb. Higher latency links may benefit from increasing this 576% further since the maximum theoretical throughput on a link is given by 577% buffer-size / latency. 578% See https://support.microsoft.com/en-gb/help/823764/slow-performance-occurs-when-you-copy-data-to-a-tcp-server-by-using-a 579% for Microsoft's discussion 580 581%! tcp_fcntl(+Stream, +Action, ?Argument) is det. 582% 583% Interface to the fcntl() call. Currently only suitable to deal 584% switch stream to non-blocking mode using: 585% 586% == 587% tcp_fcntl(Stream, setfl, nonblock), 588% == 589% 590% An attempt to read from a non-blocking stream while there is no 591% data available returns -1 (or =end_of_file= for read/1), but 592% at_end_of_stream/1 fails. On actual end-of-input, 593% at_end_of_stream/1 succeeds. 594 595tcp_fcntl(Socket, setfl, nonblock) :- 596 !, 597 tcp_setopt(Socket, nonblock). 598 599%! tcp_getopt(+Socket, ?Option) is semidet. 600% 601% Get information about Socket. Defined properties are below. 602% Requesting an unknown option results in a `domain_error` exception. 603% 604% - file_no(-File) 605% Get the OS file handle as an integer. This may be used for 606% debugging and integration. 607 608%! tcp_host_to_address(?HostName, ?Address) is det. 609% 610% Translate between a machines host-name and it's (IP-)address. If 611% HostName is an atom, it is resolved using getaddrinfo() and the 612% IP-number is unified to Address using a term of the format 613% ip(Byte1,Byte2,Byte3,Byte4). Otherwise, if Address is bound to 614% an ip(Byte1,Byte2,Byte3,Byte4) term, it is resolved by 615% gethostbyaddr() and the canonical hostname is unified with 616% HostName. 617% 618% @tbd This function should support more functionality provided by 619% gethostbyaddr, probably by adding an option-list. 620 621%! gethostname(-Hostname) is det. 622% 623% Return the canonical fully qualified name of this host. This is 624% achieved by calling gethostname() and return the canonical name 625% returned by getaddrinfo(). 626 627 628 /******************************* 629 * SOCKS * 630 *******************************/ 631 632%! negotiate_socks_connection(+DesiredEndpoint, +StreamPair) is det. 633% 634% Negotiate a connection to DesiredEndpoint over StreamPair. 635% DesiredEndpoint should be in the form of either: 636% 637% * hostname : port 638% * ip(A,B,C,D) : port 639% 640% @error socks_error(Details) if the SOCKS negotiation failed. 641 642negotiate_socks_connection(Host:Port, StreamPair):- 643 format(StreamPair, '~s', [[0x5, % Version 5 644 0x1, % 1 auth method supported 645 0x0]]), % which is 'no auth' 646 flush_output(StreamPair), 647 get_byte(StreamPair, ServerVersion), 648 get_byte(StreamPair, AuthenticationMethod), 649 ( ServerVersion =\= 0x05 650 -> throw(error(socks_error(invalid_version(5, ServerVersion)), _)) 651 ; AuthenticationMethod =:= 0xff 652 -> throw(error(socks_error(invalid_authentication_method( 653 0xff, 654 AuthenticationMethod)), _)) 655 ; true 656 ), 657 ( Host = ip(A,B,C,D) 658 -> AddressType = 0x1, % IPv4 Address 659 format(atom(Address), '~s', [[A, B, C, D]]) 660 ; AddressType = 0x3, % Domain 661 atom_length(Host, Length), 662 format(atom(Address), '~s~w', [[Length], Host]) 663 ), 664 P1 is Port /\ 0xff, 665 P2 is Port >> 8, 666 format(StreamPair, '~s~w~s', [[0x5, % Version 5 667 0x1, % Please establish a connection 668 0x0, % reserved 669 AddressType], 670 Address, 671 [P2, P1]]), 672 flush_output(StreamPair), 673 get_byte(StreamPair, _EchoedServerVersion), 674 get_byte(StreamPair, Status), 675 ( Status =:= 0 % Established! 676 -> get_byte(StreamPair, _Reserved), 677 get_byte(StreamPair, EchoedAddressType), 678 ( EchoedAddressType =:= 0x1 679 -> get_byte(StreamPair, _), % read IP4 680 get_byte(StreamPair, _), 681 get_byte(StreamPair, _), 682 get_byte(StreamPair, _) 683 ; get_byte(StreamPair, Length), % read host name 684 forall(between(1, Length, _), 685 get_byte(StreamPair, _)) 686 ), 687 get_byte(StreamPair, _), % read port 688 get_byte(StreamPair, _) 689 ; throw(error(socks_error(negotiation_rejected(Status)), _)) 690 ). 691 692 693 /******************************* 694 * MESSAGES * 695 *******************************/ 696 697/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 698The C-layer generates exceptions of the following format, where Message 699is extracted from the operating system. 700 701 error(socket_error(Code, Message), _) 702- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 703 704:- multifile 705 prolog:error_message//1. 706 707prologerror_message(socket_error(_Code, Message)) --> 708 [ 'Socket error: ~w'-[Message] ]. 709prologerror_message(socks_error(Error)) --> 710 socks_error(Error). 711prologerror_message(proxy_error(tried(Tried))) --> 712 [ 'Failed to connect using a proxy. Tried:'-[], nl], 713 proxy_tried(Tried). 714 715socks_error(invalid_version(Supported, Got)) --> 716 [ 'SOCKS: unsupported version: ~p (supported: ~p)'- 717 [ Got, Supported ] ]. 718socks_error(invalid_authentication_method(Supported, Got)) --> 719 [ 'SOCKS: unsupported authentication method: ~p (supported: ~p)'- 720 [ Got, Supported ] ]. 721socks_error(negotiation_rejected(Status)) --> 722 [ 'SOCKS: connection failed: ~p'-[Status] ]. 723 724proxy_tried([]) --> []. 725proxy_tried([H|T]) --> 726 proxy_tried(H), 727 proxy_tried(T). 728proxy_tried(error(Proxy, Error)) --> 729 [ '~w: '-[Proxy] ], 730 '$messages':translate_message(Error). 731proxy_tried(false(Proxy)) --> 732 [ '~w: failed with unspecified error'-[Proxy] ]