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minimal: raw udp
This commit is contained in:
Andy Green
parent
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commit
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4 changed files with 297 additions and 0 deletions
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@ -1,6 +1,7 @@
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|name|demonstrates|
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---|---
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minimal-raw-adopt-tcp|Shows how to have lws adopt an existing tcp socket something else had connected
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minimal-raw-adopt-udp|Shows how to create a udp socket and read and write on it
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minimal-raw-file|Shows how to adopt a file descriptor (device node, fifo, file, etc) into the lws event loop and handle events
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minimal-raw-vhost|Shows how to set up a vhost that listens and accepts RAW socket connections
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76
minimal-examples/raw/minimal-raw-adopt-udp/CMakeLists.txt
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76
minimal-examples/raw/minimal-raw-adopt-udp/CMakeLists.txt
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cmake_minimum_required(VERSION 2.8)
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include(CheckCSourceCompiles)
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set(SAMP lws-minimal-raw-adopt-udp)
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set(SRCS minimal-raw-adopt-udp.c)
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# If we are being built as part of lws, confirm current build config supports
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# reqconfig, else skip building ourselves.
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#
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# If we are being built externally, confirm installed lws was configured to
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# support reqconfig, else error out with a helpful message about the problem.
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#
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MACRO(require_lws_config reqconfig _val result)
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if (DEFINED ${reqconfig})
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if (${reqconfig})
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set (rq 1)
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else()
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set (rq 0)
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endif()
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else()
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set(rq 0)
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endif()
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if (${_val} EQUAL ${rq})
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set(SAME 1)
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else()
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set(SAME 0)
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endif()
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if (LWS_WITH_MINIMAL_EXAMPLES AND NOT ${SAME})
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if (${_val})
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message("${SAMP}: skipping as lws being built without ${reqconfig}")
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else()
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message("${SAMP}: skipping as lws built with ${reqconfig}")
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endif()
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set(${result} 0)
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else()
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if (LWS_WITH_MINIMAL_EXAMPLES)
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set(MET ${SAME})
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else()
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CHECK_C_SOURCE_COMPILES("#include <libwebsockets.h>\nint main(void) {\n#if defined(${reqconfig})\n return 0;\n#else\n fail;\n#endif\n return 0;\n}\n" HAS_${reqconfig})
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if (NOT DEFINED HAS_${reqconfig} OR NOT HAS_${reqconfig})
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set(HAS_${reqconfig} 0)
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else()
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set(HAS_${reqconfig} 1)
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endif()
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if ((HAS_${reqconfig} AND ${_val}) OR (NOT HAS_${reqconfig} AND NOT ${_val}))
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set(MET 1)
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else()
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set(MET 0)
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endif()
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endif()
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if (NOT MET)
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if (${_val})
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message(FATAL_ERROR "This project requires lws must have been configured with ${reqconfig}")
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else()
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message(FATAL_ERROR "Lws configuration of ${reqconfig} is incompatible with this project")
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endif()
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endif()
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endif()
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ENDMACRO()
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set(requirements 1)
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require_lws_config(LWS_WITHOUT_SERVER 0 requirements)
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if (requirements)
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add_executable(${SAMP} ${SRCS})
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if (websockets_shared)
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target_link_libraries(${SAMP} websockets_shared)
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add_dependencies(${SAMP} websockets_shared)
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else()
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target_link_libraries(${SAMP} websockets)
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endif()
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endif()
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49
minimal-examples/raw/minimal-raw-adopt-udp/README.md
Normal file
49
minimal-examples/raw/minimal-raw-adopt-udp/README.md
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# lws minimal ws server raw adopt udp
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This example demonstrates echoing packets on a UDP socket in lws.
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A "foreign" UDP socket is created, bound (so it can "listen"), and
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adopted into lws event loop. It acts like a tcp RAW mode connection in
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lws and uses the same callbacks.
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Writing is a bit different for UDP. By default, the system has no
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idea about the receiver state and so asking for a callback_on_writable()
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always believes that the socket is writeable... the callback will
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happen next time around the event loop if there are no pending partials.
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With UDP, there is no "connection". You need to write with sendto() and
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direct the packets to a specific destination. You can learn the source
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of the last packet that arrived at the LWS_CALLBACK_RAW_RX callback by
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getting a `struct lws_udp *` from `lws_get_udp(wsi)`. To be able to
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send back to that guy, you should take a copy of the `struct lws_udp *` and
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use the .sa and .salen members in your sendto().
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However the kernel may not accept to buffer / write everything you wanted to send.
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So you are responsible to watch the result of sendto() and resend the
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unsent part next time.
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## build
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```
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$ cmake . && make
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```
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## usage
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```
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$ ./lws-minimal-raw-adopt-udp
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$ ./lws-minimal-raw-adopt-udp
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[2018/03/24 08:12:37:8869] USER: LWS minimal raw adopt udp | nc -u 127.0.0.1 7681
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[2018/03/24 08:12:37:8870] NOTICE: Creating Vhost 'default' (no listener), 1 protocols, IPv6 off
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[2018/03/24 08:12:37:8878] USER: LWS_CALLBACK_RAW_ADOPT
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[2018/03/24 08:12:41:5656] USER: LWS_CALLBACK_RAW_RX (6)
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[2018/03/24 08:12:41:5656] NOTICE:
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[2018/03/24 08:12:41:5656] NOTICE: 0000: 68 65 6C 6C 6F 0A hello.
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[2018/03/24 08:12:41:5656] NOTICE:
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```
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```
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$ nc -u 127.0.0.1 7681
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hello
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hello
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```
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@ -0,0 +1,171 @@
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/*
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* lws-minimal-raw-adopt-udp
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*
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* Copyright (C) 2018 Andy Green <andy@warmcat.com>
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*
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* This file is made available under the Creative Commons CC0 1.0
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* Universal Public Domain Dedication.
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*
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* This demonstrates integrating a connected udp
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* socket into the lws event loop as a RAW wsi. It's interesting in
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* the kind of situation where you already have a connected socket
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* in your application, and you need to hand it over to lws to deal with.
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*
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* Lws supports "adopting" these foreign sockets, and also has a helper API
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* to create, bind, and adopt them inside lws.
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*/
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#include <libwebsockets.h>
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#include <string.h>
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#include <signal.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <errno.h>
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#include <arpa/inet.h>
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static uint8_t sendbuf[4096];
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static size_t sendlen;
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struct lws_udp udp;
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static int
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callback_raw_test(struct lws *wsi, enum lws_callback_reasons reason,
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void *user, void *in, size_t len)
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{
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ssize_t n;
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switch (reason) {
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/* callbacks related to raw socket descriptor */
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case LWS_CALLBACK_RAW_ADOPT:
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lwsl_user("LWS_CALLBACK_RAW_ADOPT\n");
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break;
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case LWS_CALLBACK_RAW_CLOSE:
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lwsl_user("LWS_CALLBACK_RAW_CLOSE\n");
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break;
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case LWS_CALLBACK_RAW_RX:
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lwsl_user("LWS_CALLBACK_RAW_RX (%d)\n", (int)len);
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lwsl_hexdump_level(LLL_NOTICE, in, len);
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/*
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* Take a copy of the buffer and the source socket address...
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*/
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udp = *(lws_get_udp(wsi));
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sendlen = len;
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if (sendlen > sizeof(sendbuf))
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sendlen = sizeof(sendbuf);
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memcpy(sendbuf, in, sendlen);
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/*
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* ... and we send it next time around the event loop. This
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* can be extended to having a ringbuffer of different send
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* buffers and targets queued.
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*
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* Note that UDP is ALWAYS writable as far as poll() knows
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* because there is no mechanism like the tcp window to
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* understand that packets are not being acknowledged. But
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* this allows the event loop to share out the work.
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*/
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lws_callback_on_writable(wsi);
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break;
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case LWS_CALLBACK_RAW_WRITEABLE:
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if (!sendlen)
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break;
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/*
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* We can write directly on the UDP socket, specifying
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* the peer the write is directed to.
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*
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* However the kernel may only accept parts of large sendto()s,
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* leaving you to try to resend the remainder later. However
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* depending on how your protocol on top of UDP works, that
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* may involve sticking new headers before the remainder.
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*
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* For clarity partial sends just drop the remainder here.
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*/
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n = sendto(lws_get_socket_fd(wsi), sendbuf, sendlen, 0, &udp.sa,
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udp.salen);
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if (n < (ssize_t)len)
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lwsl_notice("%s: send returned %d\n", __func__, (int)n);
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break;
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default:
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break;
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}
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return 0;
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}
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static struct lws_protocols protocols[] = {
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{ "raw-test", callback_raw_test, 0, 0 },
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{ NULL, NULL, 0, 0 } /* terminator */
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};
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static int interrupted;
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void sigint_handler(int sig)
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{
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interrupted = 1;
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}
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int main(int argc, char **argv)
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{
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struct lws_context_creation_info info;
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struct lws_context *context;
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struct lws_vhost *vhost;
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int n = 0;
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lws_set_log_level(LLL_USER | LLL_ERR | LLL_WARN | LLL_NOTICE
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/* for LLL_ verbosity above NOTICE to be built into lws,
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* lws must have been configured and built with
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* -DCMAKE_BUILD_TYPE=DEBUG instead of =RELEASE */
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/* | LLL_INFO */ /* | LLL_PARSER */ /* | LLL_HEADER */
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/* | LLL_EXT */ /* | LLL_CLIENT */ /* | LLL_LATENCY */
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/* | LLL_DEBUG */, NULL);
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memset(&info, 0, sizeof info); /* otherwise uninitialized garbage */
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info.options = LWS_SERVER_OPTION_EXPLICIT_VHOSTS;
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lwsl_user("LWS minimal raw adopt udp | nc -u 127.0.0.1 7681\n");
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signal(SIGINT, sigint_handler);
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context = lws_create_context(&info);
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if (!context) {
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lwsl_err("lws init failed\n");
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return 1;
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}
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info.port = CONTEXT_PORT_NO_LISTEN_SERVER;
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info.protocols = protocols;
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vhost = lws_create_vhost(context, &info);
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if (!vhost) {
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lwsl_err("lws vhost creation failed\n");
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goto bail;
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}
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/*
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* Create our own "foreign" UDP socket bound to 7681/udp
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*/
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if (!lws_create_adopt_udp(vhost, 7681, LWS_CAUDP_BIND,
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protocols[0].name, NULL)) {
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lwsl_err("%s: foreign socket adoption failed\n", __func__);
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goto bail;
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}
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while (n >= 0 && !interrupted)
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n = lws_service(context, 1000);
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bail:
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lws_context_destroy(context);
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return 0;
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}
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