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) 2000-2016, University of Amsterdam 7 VU University Amsterdam 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 17 2. Redistributions in binary form must reproduce the above copyright 18 notice, this list of conditions and the following disclaimer in 19 the documentation and/or other materials provided with the 20 distribution. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 30 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 32 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 POSSIBILITY OF SUCH DAMAGE. 34*/ 35 36:- module(socket, 37 [ tcp_socket/1, % -Socket 38 tcp_close_socket/1, % +Socket 39 tcp_open_socket/3, % +Socket, -Read, -Write 40 tcp_connect/2, % +Socket, +Address 41 tcp_connect/3, % +Socket, +Address, -StreamPair 42 tcp_connect/4, % +Socket, +Address, -Read, -Write) 43 tcp_bind/2, % +Socket, +Address 44 tcp_accept/3, % +Master, -Slave, -PeerName 45 tcp_listen/2, % +Socket, +BackLog 46 tcp_fcntl/3, % +Socket, +Command, ?Arg 47 tcp_setopt/2, % +Socket, +Option 48 tcp_host_to_address/2, % ?HostName, ?Ip-nr 49 tcp_select/3, % +Inputs, -Ready, +Timeout 50 gethostname/1, % -HostName 51 52 tcp_open_socket/2, % +Socket, -StreamPair 53 54 udp_socket/1, % -Socket 55 udp_receive/4, % +Socket, -Data, -Sender, +Options 56 udp_send/4, % +Socket, +Data, +Sender, +Options 57 58 negotiate_socks_connection/2% +DesiredEndpoint, +StreamPair 59 ]). 60:- use_module(library(shlib)). 61:- use_module(library(debug)). 62:- use_module(library(lists)). 63 64/** <module> Network socket (TCP and UDP) library 65 66The library(socket) provides TCP and UDP inet-domain sockets from 67SWI-Prolog, both client and server-side communication. The interface of 68this library is very close to the Unix socket interface, also supported 69by the MS-Windows _winsock_ API. SWI-Prolog applications that wish to 70communicate with multiple sources have three options: 71 72 - Use I/O multiplexing based on wait_for_input/3. On Windows 73 systems this can only be used for sockets, not for general 74 (device-) file handles. 75 - Use multiple threads, handling either a single blocking socket 76 or a pool using I/O multiplexing as above. 77 - Using XPCE's class `socket` which synchronises socket 78 events in the GUI event-loop. 79 80## Client applications {#socket-server} 81 82Using this library to establish a TCP connection to a server is as 83simple as opening a file. See also http_open/3. 84 85== 86dump_swi_homepage :- 87 setup_call_cleanup( 88 tcp_connect(www.swi-prolog.org:http, Stream, []), 89 ( format(Stream, 90 'GET / HTTP/1.1~n\c 91 Host: www.swi-prolog.org~n\c 92 Connection: close~n~n', []), 93 flush_output(Stream), 94 copy_stream_data(Stream, current_output) 95 ), 96 close(S)). 97== 98 99To deal with timeouts and multiple connections, threads, 100wait_for_input/3 and/or non-blocking streams (see tcp_fcntl/3) can be 101used. 102 103## Server applications {#socket-client} 104 105The typical sequence for generating a server application is given below. 106To close the server, use close/1 on `AcceptFd`. 107 108 == 109 create_server(Port) :- 110 tcp_socket(Socket), 111 tcp_bind(Socket, Port), 112 tcp_listen(Socket, 5), 113 tcp_open_socket(Socket, AcceptFd, _), 114 <dispatch> 115 == 116 117There are various options for <dispatch>. The most commonly used option 118is to start a Prolog thread to handle the connection. Alternatively, 119input from multiple clients can be handled in a single thread by 120listening to these clients using wait_for_input/3. Finally, on Unix 121systems, we can use fork/1 to handle the connection in a new process. 122Note that fork/1 and threads do not cooperate well. Combinations can be 123realised but require good understanding of POSIX thread and 124fork-semantics. 125 126Below is the typical example using a thread. Note the use of 127setup_call_cleanup/3 to guarantee that all resources are reclaimed, also 128in case of failure or exceptions. 129 130 == 131 dispatch(AcceptFd) :- 132 tcp_accept(AcceptFd, Socket, _Peer), 133 thread_create(process_client(Socket, Peer), _, 134 [ detached(true) 135 ]), 136 dispatch(AcceptFd). 137 138 process_client(Socket, Peer) :- 139 setup_call_cleanup( 140 tcp_open_socket(Socket, StreamPair), 141 handle_service(In, StreamPair), 142 close(StreamPair)). 143 144 handle_service(StreamPair) :- 145 ... 146 == 147 148## TCP socket predicates {#socket-predicates} 149*/ 150 151:- multifile 152 tcp_connect_hook/3, % +Socket, +Addr, -In, -Out 153 tcp_connect_hook/4, % +Socket, +Addr, -Stream 154 proxy_for_url/3, % +URL, +Host, -ProxyList 155 try_proxy/4. % +Proxy, +Addr, -Socket, -Stream 156 157:- predicate_options(tcp_connect/3, 3, 158 [ bypass_proxy(boolean), 159 nodelay(boolean) 160 ]). 161 162:- use_foreign_library(foreign(socket), install_socket). 163:- public tcp_debug/1. % set debugging. 164 165%! tcp_socket(-SocketId) is det. 166% 167% Creates an INET-domain stream-socket and unifies an identifier 168% to it with SocketId. On MS-Windows, if the socket library is not 169% yet initialised, this will also initialise the library. 170 171%! tcp_close_socket(+SocketId) is det. 172% 173% Closes the indicated socket, making SocketId invalid. Normally, 174% sockets are closed by closing both stream handles returned by 175% open_socket/3. There are two cases where tcp_close_socket/1 is 176% used because there are no stream-handles: 177% 178% - If, after tcp_accept/3, the server uses fork/1 to handle the 179% client in a sub-process. In this case the accepted socket is 180% not longer needed from the main server and must be discarded 181% using tcp_close_socket/1. 182% - If, after discovering the connecting client with 183% tcp_accept/3, the server does not want to accept the 184% connection, it should discard the accepted socket 185% immediately using tcp_close_socket/1. 186 187%! tcp_open_socket(+SocketId, -StreamPair) is det. 188% 189% Create streams to communicate to SocketId. If SocketId is a 190% master socket (see tcp_bind/2), StreamPair should be used for 191% tcp_accept/3. If SocketId is a connected (see tcp_connect/2) or 192% accepted socket (see tcp_accept/3), StreamPair is unified to a 193% stream pair (see stream_pair/3) that can be used for reading and 194% writing. The stream or pair must be closed with close/1, which 195% also closes SocketId. 196 197tcp_open_socket(Socket, Stream) :- 198 tcp_open_socket(Socket, In, Out), 199 ( var(Out) 200 -> Stream = In 201 ; stream_pair(Stream, In, Out) 202 ). 203 204%! tcp_open_socket(+SocketId, -InStream, -OutStream) is det. 205% 206% Similar to tcp_open_socket/2, but creates two separate sockets 207% where tcp_open_socket/2 would have created a stream pair. 208% 209% @deprecated New code should use tcp_open_socket/2 because 210% closing a stream pair is much easier to perform safely. 211 212%! tcp_bind(SocketId, ?Address) is det. 213% 214% Bind the socket to Address on the current machine. This 215% operation, together with tcp_listen/2 and tcp_accept/3 implement 216% the _server-side_ of the socket interface. Address is either an 217% plain `Port` or a term HostPort. The first form binds the socket 218% to the given port on all interfaces, while the second only binds 219% to the matching interface. A typical example is below, causing 220% the socket to listen only on port 8080 on the local machine's 221% network. 222% 223% == 224% tcp_bind(Socket, localhost:8080) 225% == 226% 227% If `Port` is unbound, the system picks an arbitrary free port 228% and unifies `Port` with the selected port number. `Port` is 229% either an integer or the name of a registered service. See also 230% tcp_connect/4. 231 232%! tcp_listen(+SocketId, +BackLog) is det. 233% 234% Tells, after tcp_bind/2, the socket to listen for incoming 235% requests for connections. Backlog indicates how many pending 236% connection requests are allowed. Pending requests are requests 237% that are not yet acknowledged using tcp_accept/3. If the 238% indicated number is exceeded, the requesting client will be 239% signalled that the service is currently not available. A 240% commonly used default value for Backlog is 5. 241 242%! tcp_accept(+Socket, -Slave, -Peer) is det. 243% 244% This predicate waits on a server socket for a connection request 245% by a client. On success, it creates a new socket for the client 246% and binds the identifier to Slave. Peer is bound to the 247% IP-address of the client. 248 249%! tcp_connect(+SocketId, +HostAndPort) is det. 250% 251% Connect SocketId. After successful completion, tcp_open_socket/3 252% can be used to create I/O-Streams to the remote socket. This 253% predicate is part of the low level client API. A connection to a 254% particular host and port is realised using these steps: 255% 256% == 257% tcp_socket(Socket), 258% tcp_connect(Socket, Host:Port), 259% tcp_open_socket(Socket, StreamPair) 260% == 261% 262% Typical client applications should use the high level interface 263% provided by tcp_connect/3 which avoids resource leaking if a 264% step in the process fails, and can be hooked to support proxies. 265% For example: 266% 267% == 268% setup_call_cleanup( 269% tcp_connect(Host:Port, StreamPair, []), 270% talk(StreamPair), 271% close(StreamPair)) 272% == 273 274 275 /******************************* 276 * HOOKABLE CONNECT * 277 *******************************/ 278 279%! tcp_connect(+Socket, +Address, -Read, -Write) is det. 280% 281% Connect a (client) socket to Address and return a bi-directional 282% connection through the stream-handles Read and Write. This 283% predicate may be hooked by defining socket:tcp_connect_hook/4 284% with the same signature. Hooking can be used to deal with proxy 285% connections. E.g., 286% 287% == 288% :- multifile socket:tcp_connect_hook/4. 289% 290% socket:tcp_connect_hook(Socket, Address, Read, Write) :- 291% proxy(ProxyAdress), 292% tcp_connect(Socket, ProxyAdress), 293% tcp_open_socket(Socket, Read, Write), 294% proxy_connect(Address, Read, Write). 295% == 296% 297% @deprecated New code should use tcp_connect/3 called as 298% tcp_connect(+Address, -StreamPair, +Options). 299 300tcp_connect(Socket, Address, Read, Write) :- 301 tcp_connect_hook(Socket, Address, Read, Write), 302 !. 303tcp_connect(Socket, Address, Read, Write) :- 304 tcp_connect(Socket, Address), 305 tcp_open_socket(Socket, Read, Write). 306 307 308 309%! tcp_connect(+Address, -StreamPair, +Options) is det. 310%! tcp_connect(+Socket, +Address, -StreamPair) is det. 311% 312% Establish a TCP communication as a client. The +,-,+ mode is the 313% preferred way for a client to establish a connection. This 314% predicate can be hooked to support network proxies. To use a 315% proxy, the hook proxy_for_url/3 must be defined. Permitted 316% options are: 317% 318% * bypass_proxy(+Boolean) 319% Defaults to =false=. If =true=, do not attempt to use any 320% proxies to obtain the connection 321% 322% * nodelay(+Boolean) 323% Defaults to =false=. If =true=, set nodelay on the 324% resulting socket using tcp_setopt(Socket, nodelay) 325% 326% The +,+,- mode is deprecated and does not support proxies. It 327% behaves like tcp_connect/4, but creates a stream pair (see 328% stream_pair/3). 329% 330% @error proxy_error(tried(ResultList)) is raised by mode (+,-,+) 331% if proxies are defines by proxy_for_url/3 but no proxy can 332% establsh the connection. `ResultList` contains one or more terms 333% of the form false(Proxy) for a hook that simply failed or 334% error(Proxy, ErrorTerm) for a hook that raised an exception. 335% 336% @see library(http/http_proxy) defines a hook that allows to 337% connect through HTTP proxies that support the =CONNECT= method. 338 339% Main mode: +,-,+ 340tcp_connect(Address, StreamPair, Options) :- 341 var(StreamPair), 342 !, 343 ( memberchk(bypass_proxy(true), Options) 344 -> tcp_connect_direct(Address, Socket, StreamPair) 345 ; findall(Result, 346 try_a_proxy(Address, Result), 347 ResultList), 348 last(ResultList, Status) 349 -> ( Status = true(_Proxy, Socket, StreamPair) 350 -> true 351 ; throw(error(proxy_error(tried(ResultList)), _)) 352 ) 353 ; tcp_connect_direct(Address, Socket, StreamPair) 354 ), 355 ( memberchk(nodelay(true), Options) 356 -> tcp_setopt(Socket, nodelay) 357 ; true 358 ). 359% backward compatibility mode +,+,- 360tcp_connect(Socket, Address, StreamPair) :- 361 tcp_connect_hook(Socket, Address, StreamPair0), 362 !, 363 StreamPair = StreamPair0. 364tcp_connect(Socket, Address, StreamPair) :- 365 tcp_connect(Socket, Address, Read, Write), 366 stream_pair(StreamPair, Read, Write). 367 368 369tcp_connect_direct(Address, Socket, StreamPair):- 370 tcp_socket(Socket), 371 catch(tcp_connect(Socket, Address, StreamPair), 372 Error, 373 ( tcp_close_socket(Socket), 374 throw(Error) 375 )). 376 377%! tcp_select(+ListOfStreams, -ReadyList, +TimeOut) 378% 379% Same as the built-in wait_for_input/3, but integrates better 380% with event processing and the various options of sockets for 381% Windows. On non-windows systems this simply calls 382% wait_for_input/3. 383 384:- if(\+predicate_property(tcp_select(_,_,_), defined)). 385tcp_select(ListOfStreams, ReadyList, TimeOut) :- 386 wait_for_input(ListOfStreams, ReadyList, TimeOut). 387:- endif. 388 389 390 /******************************* 391 * PROXY SUPPORT * 392 *******************************/ 393 394try_a_proxy(Address, Result) :- 395 format(atom(URL), 'socket://~w', [Address]), 396 ( Address = Host:_ 397 -> true 398 ; Host = Address 399 ), 400 proxy_for_url(URL, Host, Proxy), 401 debug(socket(proxy), 'Socket connecting via ~w~n', [Proxy]), 402 ( catch(try_proxy(Proxy, Address, Socket, Stream), E, true) 403 -> ( var(E) 404 -> !, Result = true(Proxy, Socket, Stream) 405 ; Result = error(Proxy, E) 406 ) 407 ; Result = false(Proxy) 408 ), 409 debug(socket(proxy), 'Socket: ~w: ~p', [Proxy, Result]). 410 411%! try_proxy(+Proxy, +TargetAddress, -Socket, -StreamPair) is semidet. 412% 413% Attempt a socket-level connection via the given proxy to 414% TargetAddress. The Proxy argument must match the output argument 415% of proxy_for_url/3. The predicate tcp_connect/3 (and http_open/3 416% from the library(http/http_open)) collect the results of failed 417% proxies and raise an exception no proxy is capable of realizing 418% the connection. 419% 420% The default implementation recognises the values for Proxy 421% described below. The library(http/http_proxy) adds 422% proxy(Host,Port) which allows for HTTP proxies using the 423% =CONNECT= method. 424% 425% - direct 426% Do not use any proxy 427% - socks(Host, Port) 428% Use a SOCKS5 proxy 429 430:- multifile 431 try_proxy/4. 432 433try_proxy(direct, Address, Socket, StreamPair) :- 434 !, 435 tcp_connect_direct(Address, Socket, StreamPair). 436try_proxy(socks(Host, Port), Address, Socket, StreamPair) :- 437 !, 438 tcp_connect_direct(Host:Port, Socket, StreamPair), 439 catch(negotiate_socks_connection(Address, StreamPair), 440 Error, 441 ( close(StreamPair, [force(true)]), 442 throw(Error) 443 )). 444 445%! proxy_for_url(+URL, +Hostname, -Proxy) is nondet. 446% 447% This hook can be implemented to return a proxy to try when 448% connecting to URL. Returned proxies are tried in the order in 449% which they are returned by the multifile hook try_proxy/4. 450% Pre-defined proxy methods are: 451% 452% * direct 453% connect directly to the resource 454% * proxy(Host, Port) 455% Connect to the resource using an HTTP proxy. If the 456% resource is not an HTTP URL, then try to connect using the 457% CONNECT verb, otherwise, use the GET verb. 458% * socks(Host, Port) 459% Connect to the resource via a SOCKS5 proxy 460% 461% These correspond to the proxy methods defined by PAC [Proxy 462% auto-config](http://en.wikipedia.org/wiki/Proxy_auto-config). 463% Additional methods can be returned if suitable clauses for 464% http:http_connection_over_proxy/6 or try_proxy/4 are defined. 465 466:- multifile 467 proxy_for_url/3. 468 469 470 /******************************* 471 * OPTIONS * 472 *******************************/ 473 474%! tcp_setopt(+SocketId, +Option) is det. 475% 476% Set options on the socket. Defined options are: 477% 478% - reuseaddr 479% Allow servers to reuse a port without the system being 480% completely sure the port is no longer in use. 481% 482% - bindtodevice(+Device) 483% Bind the socket to Device (an atom). For example, the code 484% below binds the socket to the _loopback_ device that is 485% typically used to realise the _localhost_. See the manual 486% pages for setsockopt() and the socket interface (e.g., 487% socket(7) on Linux) for details. 488% 489% == 490% tcp_socket(Socket), 491% tcp_setopt(Socket, bindtodevice(lo)) 492% == 493% 494% - nodelay 495% - nodelay(true) 496% If =true=, disable the Nagle optimization on this socket, 497% which is enabled by default on almost all modern TCP/IP 498% stacks. The Nagle optimization joins small packages, which is 499% generally desirable, but sometimes not. Please note that the 500% underlying TCP_NODELAY setting to setsockopt() is not 501% available on all platforms and systems may require additional 502% privileges to change this option. If the option is not 503% supported, tcp_setopt/2 raises a domain_error exception. See 504% [Wikipedia](http://en.wikipedia.org/wiki/Nagle's_algorithm) 505% for details. 506% 507% - broadcast 508% UDP sockets only: broadcast the package to all addresses 509% matching the address. The address is normally the address of 510% the local subnet (i.e. 192.168.1.255). See udp_send/4. 511% 512% - dispatch(+Boolean) 513% In GUI environments (using XPCE or the Windows =swipl-win.exe= 514% executable) this flags defines whether or not any events are 515% dispatched on behalf of the user interface. Default is 516% =true=. Only very specific situations require setting 517% this to =false=. 518 519%! tcp_fcntl(+Stream, +Action, ?Argument) is det. 520% 521% Interface to the fcntl() call. Currently only suitable to deal 522% switch stream to non-blocking mode using: 523% 524% == 525% tcp_fcntl(Stream, setfl, nonblock), 526% == 527% 528% An attempt to read from a non-blocking stream while there is no 529% data available returns -1 (or =end_of_file= for read/1), but 530% at_end_of_stream/1 fails. On actual end-of-input, 531% at_end_of_stream/1 succeeds. 532 533tcp_fcntl(Socket, setfl, nonblock) :- 534 !, 535 tcp_setopt(Socket, nonblock). 536 537%! tcp_host_to_address(?HostName, ?Address) is det. 538% 539% Translate between a machines host-name and it's (IP-)address. If 540% HostName is an atom, it is resolved using getaddrinfo() and the 541% IP-number is unified to Address using a term of the format 542% ip(Byte1,Byte2,Byte3,Byte4). Otherwise, if Address is bound to 543% an ip(Byte1,Byte2,Byte3,Byte4) term, it is resolved by 544% gethostbyaddr() and the canonical hostname is unified with 545% HostName. 546% 547% @tbd This function should support more functionality provided by 548% gethostbyaddr, probably by adding an option-list. 549 550%! gethostname(-Hostname) is det. 551% 552% Return the canonical fully qualified name of this host. This is 553% achieved by calling gethostname() and return the canonical name 554% returned by getaddrinfo(). 555 556 557 /******************************* 558 * SOCKS * 559 *******************************/ 560 561%! negotiate_socks_connection(+DesiredEndpoint, +StreamPair) is det. 562% 563% Negotiate a connection to DesiredEndpoint over StreamPair. 564% DesiredEndpoint should be in the form of either: 565% 566% * hostname : port 567% * ip(A,B,C,D) : port 568% 569% @error socks_error(Details) if the SOCKS negotiation failed. 570 571negotiate_socks_connection(Host:Port, StreamPair):- 572 format(StreamPair, '~s', [[0x5, % Version 5 573 0x1, % 1 auth method supported 574 0x0]]), % which is 'no auth' 575 flush_output(StreamPair), 576 get_byte(StreamPair, ServerVersion), 577 get_byte(StreamPair, AuthenticationMethod), 578 ( ServerVersion =\= 0x05 579 -> throw(error(socks_error(invalid_version(5, ServerVersion)), _)) 580 ; AuthenticationMethod =:= 0xff 581 -> throw(error(socks_error(invalid_authentication_method( 582 0xff, 583 AuthenticationMethod)), _)) 584 ; true 585 ), 586 ( Host = ip(A,B,C,D) 587 -> AddressType = 0x1, % IPv4 Address 588 format(atom(Address), '~s', [[A, B, C, D]]) 589 ; AddressType = 0x3, % Domain 590 atom_length(Host, Length), 591 format(atom(Address), '~s~w', [[Length], Host]) 592 ), 593 P1 is Port /\ 0xff, 594 P2 is Port >> 8, 595 format(StreamPair, '~s~w~s', [[0x5, % Version 5 596 0x1, % Please establish a connection 597 0x0, % reserved 598 AddressType], 599 Address, 600 [P2, P1]]), 601 flush_output(StreamPair), 602 get_byte(StreamPair, _EchoedServerVersion), 603 get_byte(StreamPair, Status), 604 ( Status =:= 0 % Established! 605 -> get_byte(StreamPair, _Reserved), 606 get_byte(StreamPair, EchoedAddressType), 607 ( EchoedAddressType =:= 0x1 608 -> get_byte(StreamPair, _), % read IP4 609 get_byte(StreamPair, _), 610 get_byte(StreamPair, _), 611 get_byte(StreamPair, _) 612 ; get_byte(StreamPair, Length), % read host name 613 forall(between(1, Length, _), 614 get_byte(StreamPair, _)) 615 ), 616 get_byte(StreamPair, _), % read port 617 get_byte(StreamPair, _) 618 ; throw(error(socks_error(negotiation_rejected(Status)), _)) 619 ). 620 621 622 /******************************* 623 * MESSAGES * 624 *******************************/ 625 626/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 627The C-layer generates exceptions of the following format, where Message 628is extracted from the operating system. 629 630 error(socket_error(Message), _) 631- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 632 633:- multifile 634 prolog:error_message//1. 635 636prologerror_message(socket_error(Message)) --> 637 [ 'Socket error: ~w'-[Message] ]. 638prologerror_message(socks_error(Error)) --> 639 socks_error(Error). 640prologerror_message(proxy_error(tried(Tried))) --> 641 [ 'Failed to connect using a proxy. Tried:'-[], nl], 642 proxy_tried(Tried). 643 644socks_error(invalid_version(Supported, Got)) --> 645 [ 'SOCKS: unsupported version: ~p (supported: ~p)'- 646 [ Got, Supported ] ]. 647socks_error(invalid_authentication_method(Supported, Got)) --> 648 [ 'SOCKS: unsupported authentication method: ~p (supported: ~p)'- 649 [ Got, Supported ] ]. 650socks_error(negotiation_rejected(Status)) --> 651 [ 'SOCKS: connection failed: ~p'-[Status] ]. 652 653proxy_tried([]) --> []. 654proxy_tried([H|T]) --> 655 proxy_tried(H), 656 proxy_tried(T). 657proxy_tried(error(Proxy, Error)) --> 658 [ '~w: '-[Proxy] ], 659 '$messages':translate_message(Error). 660proxy_tried(false(Proxy)) --> 661 [ '~w: failed with unspecified error'-[Proxy] ].