| src/examples/cpp03/fork/daemon.cpp | src/examples/cpp11/fork/daemon.cpp |
|---|
| ⋮ | ⋮ |
| 1 | // | 1 | // |
| 2 | //·daemon.cpp | 2 | //·daemon.cpp |
| 3 | //·~~~~~~~~~~ | 3 | //·~~~~~~~~~~ |
| 4 | // | 4 | // |
| 5 | //·Copyright·(c)·2003-2020·Christopher·M.·Kohlhoff·(chris·at·kohlhoff·dot·com) | 5 | //·Copyright·(c)·2003-2020·Christopher·M.·Kohlhoff·(chris·at·kohlhoff·dot·com) |
| 6 | // | 6 | // |
| 7 | //·Distributed·under·the·Boost·Software·License,·Version·1.0.·(See·accompanying | 7 | //·Distributed·under·the·Boost·Software·License,·Version·1.0.·(See·accompanying |
| 8 | //·file·LICENSE_1_0.txt·or·copy·at·http://www.boost.org/LICENSE_1_0.txt) | 8 | //·file·LICENSE_1_0.txt·or·copy·at·http://www.boost.org/LICENSE_1_0.txt) |
| 9 | // | 9 | // |
| 10 | | 10 | |
| 11 | #include·<asio/io_context.hpp> | 11 | #include·<asio/io_context.hpp> |
| 12 | #include·<asio/ip/udp.hpp> | 12 | #include·<asio/ip/udp.hpp> |
| 13 | #include·<asio/signal_set.hpp> | 13 | #include·<asio/signal_set.hpp> |
| 14 | #include·<boost/array.hpp> | 14 | #include·<array> |
| 15 | #include·<boost/bind/bind.hpp> | |
| 16 | #include·<ctime> | 15 | #include·<ctime> |
| 17 | #include·<iostream> | 16 | #include·<iostream> |
| 18 | #include·<syslog.h> | 17 | #include·<syslog.h> |
| 19 | #include·<unistd.h> | 18 | #include·<unistd.h> |
| 20 | | 19 | |
| 21 | using·asio::ip::udp; | 20 | using·asio::ip::udp; |
| 22 | | 21 | |
| 23 | class·udp_daytime_server | 22 | class·udp_daytime_server |
| 24 | { | 23 | { |
| 25 | public: | 24 | public: |
| 26 | ··udp_daytime_server(asio::io_context&·io_context) | 25 | ··udp_daytime_server(asio::io_context&·io_context) |
| 27 | ····:·socket_(io_context,·udp::endpoint(udp::v4(),·13)) | 26 | ····:·socket_(io_context,·{udp::v4(),·13}) |
| 28 | ··{ | 27 | ··{ |
| 29 | ····start_receive(); | 28 | ····receive(); |
| 30 | ··} | 29 | ··} |
| 31 | | 30 | |
| 32 | private: | 31 | private: |
| 33 | ··void·start_receive() | 32 | ··void·receive() |
| 34 | ··{ | 33 | ··{ |
| 35 | ····socket_.async_receive_from( | 34 | ····socket_.async_receive_from( |
| 36 | ········asio::buffer(recv_buffer_),·remote_endpoint_, | 35 | ········asio::buffer(recv_buffer_),·remote_endpoint_, |
| 37 | ········boost::bind(&udp_daytime_server::handle_receive, | 36 | ········[this](std::error_code·ec,·std::size_t·/*n*/) |
| 38 | ··········this,·boost::placeholders::_1)); | 37 | ········{ |
| 39 | ··} | 38 | ··········if·(!ec) |
| 40 | | 39 | ··········{ |
| 41 | ··void·handle_receive(const·asio::error_code&·ec) | 40 | ············using·namespace·std;·//·For·time_t,·time·and·ctime; |
| 42 | ··{ | 41 | ············time_t·now·=·time(0); |
| 43 | ····if·(!ec) | 42 | ············std::string·message·=·ctime(&now); |
| 44 | ····{ | 43 | |
| 45 | ······using·namespace·std;·//·For·time_t,·time·and·ctime; | 44 | ············std::error_code·ignored_ec; |
| 46 | ······time_t·now·=·time(0); | 45 | ············socket_.send_to(asio::buffer(message), |
| 47 | ······std::string·message·=·ctime(&now); | 46 | ················remote_endpoint_,·0,·ignored_ec); |
| 48 | | 47 | ··········} |
| 49 | ······asio::error_code·ignored_ec; | |
| 50 | ······socket_.send_to(asio::buffer(message), | |
| 51 | ··········remote_endpoint_,·0,·ignored_ec); | |
| 52 | ····} | |
| 53 | | 48 | |
| 54 | ····start_receive(); | 49 | ··········receive(); |
| | 50 | ········}); |
| 55 | ··} | 51 | ··} |
| 56 | | 52 | |
| 57 | ··udp::socket·socket_; | 53 | ··udp::socket·socket_; |
| 58 | ··udp::endpoint·remote_endpoint_; | 54 | ··udp::endpoint·remote_endpoint_; |
| 59 | ··boost::array<char,·1>·recv_buffer_; | 55 | ··std::array<char,·1>·recv_buffer_; |
| 60 | }; | 56 | }; |
| 61 | | 57 | |
| 62 | int·main() | 58 | int·main() |
| 63 | { | 59 | { |
| 64 | ··try | 60 | ··try |
| 65 | ··{ | 61 | ··{ |
| 66 | ····asio::io_context·io_context; | 62 | ····asio::io_context·io_context; |
| 67 | | 63 | |
| 68 | ····//·Initialise·the·server·before·becoming·a·daemon.·If·the·process·is | 64 | ····//·Initialise·the·server·before·becoming·a·daemon.·If·the·process·is |
| 69 | ····//·started·from·a·shell,·this·means·any·errors·will·be·reported·back·to·the | 65 | ····//·started·from·a·shell,·this·means·any·errors·will·be·reported·back·to·the |
| 70 | ····//·user. | 66 | ····//·user. |
| 71 | ····udp_daytime_server·server(io_context); | 67 | ····udp_daytime_server·server(io_context); |
| 72 | | 68 | |
| 73 | ····//·Register·signal·handlers·so·that·the·daemon·may·be·shut·down.·You·may | 69 | ····//·Register·signal·handlers·so·that·the·daemon·may·be·shut·down.·You·may |
| 74 | ····//·also·want·to·register·for·other·signals,·such·as·SIGHUP·to·trigger·a | 70 | ····//·also·want·to·register·for·other·signals,·such·as·SIGHUP·to·trigger·a |
| 75 | ····//·re-read·of·a·configuration·file. | 71 | ····//·re-read·of·a·configuration·file. |
| 76 | ····asio::signal_set·signals(io_context,·SIGINT,·SIGTERM); | 72 | ····asio::signal_set·signals(io_context,·SIGINT,·SIGTERM); |
| 77 | ····signals.async_wait( | 73 | ····signals.async_wait( |
| 78 | ········boost::bind(&asio::io_context::stop,·&io_context)); | 74 | ········[&](std::error_code·/*ec*/,·int·/*signo*/) |
| | 75 | ········{ |
| | 76 | ··········io_context.stop(); |
| | 77 | ········}); |
| 79 | | 78 | |
| 80 | ····//·Inform·the·io_context·that·we·are·about·to·become·a·daemon.·The | 79 | ····//·Inform·the·io_context·that·we·are·about·to·become·a·daemon.·The |
| 81 | ····//·io_context·cleans·up·any·internal·resources,·such·as·threads,·that·may | 80 | ····//·io_context·cleans·up·any·internal·resources,·such·as·threads,·that·may |
| 82 | ····//·interfere·with·forking. | 81 | ····//·interfere·with·forking. |
| 83 | ····io_context.notify_fork(asio::io_context::fork_prepare); | 82 | ····io_context.notify_fork(asio::io_context::fork_prepare); |
| 84 | | 83 | |
| 85 | ····//·Fork·the·process·and·have·the·parent·exit.·If·the·process·was·started | 84 | ····//·Fork·the·process·and·have·the·parent·exit.·If·the·process·was·started |
| 86 | ····//·from·a·shell,·this·returns·control·to·the·user.·Forking·a·new·process·is | 85 | ····//·from·a·shell,·this·returns·control·to·the·user.·Forking·a·new·process·is |
| 87 | ····//·also·a·prerequisite·for·the·subsequent·call·to·setsid(). | 86 | ····//·also·a·prerequisite·for·the·subsequent·call·to·setsid(). |
| 88 | ····if·(pid_t·pid·=·fork()) | 87 | ····if·(pid_t·pid·=·fork()) |
| 89 | ····{ | 88 | ····{ |
| 90 | ······if·(pid·>·0) | 89 | ······if·(pid·>·0) |
| 91 | ······{ | 90 | ······{ |
| 92 | ········//·We're·in·the·parent·process·and·need·to·exit. | 91 | ········//·We're·in·the·parent·process·and·need·to·exit. |
| 93 | ········// | 92 | ········// |
| 94 | ········//·When·the·exit()·function·is·used,·the·program·terminates·without | 93 | ········//·When·the·exit()·function·is·used,·the·program·terminates·without |
| 95 | ········//·invoking·local·variables'·destructors.·Only·global·variables·are | 94 | ········//·invoking·local·variables'·destructors.·Only·global·variables·are |
| 96 | ········//·destroyed.·As·the·io_context·object·is·a·local·variable,·this·means | 95 | ········//·destroyed.·As·the·io_context·object·is·a·local·variable,·this·means |
| 97 | ········//·we·do·not·have·to·call: | 96 | ········//·we·do·not·have·to·call: |
| 98 | ········// | 97 | ········// |
| 99 | ········//···io_context.notify_fork(asio::io_context::fork_parent); | 98 | ········//···io_context.notify_fork(asio::io_context::fork_parent); |
| 100 | ········// | 99 | ········// |
| 101 | ········//·However,·this·line·should·be·added·before·each·call·to·exit()·if | 100 | ········//·However,·this·line·should·be·added·before·each·call·to·exit()·if |
| 102 | ········//·using·a·global·io_context·object.·An·additional·call: | 101 | ········//·using·a·global·io_context·object.·An·additional·call: |
| 103 | ········// | 102 | ········// |
| 104 | ········//···io_context.notify_fork(asio::io_context::fork_prepare); | 103 | ········//···io_context.notify_fork(asio::io_context::fork_prepare); |
| 105 | ········// | 104 | ········// |
| 106 | ········//·should·also·precede·the·second·fork(). | 105 | ········//·should·also·precede·the·second·fork(). |
| 107 | ········exit(0); | 106 | ········exit(0); |
| 108 | ······} | 107 | ······} |
| 109 | ······else | 108 | ······else |
| 110 | ······{ | 109 | ······{ |
| 111 | ········syslog(LOG_ERR·|·LOG_USER,·"First·fork·failed:·%m"); | 110 | ········syslog(LOG_ERR·|·LOG_USER,·"First·fork·failed:·%m"); |
| 112 | ········return·1; | 111 | ········return·1; |
| 113 | ······} | 112 | ······} |
| 114 | ····} | 113 | ····} |
| 115 | | 114 | |
| 116 | ····//·Make·the·process·a·new·session·leader.·This·detaches·it·from·the | 115 | ····//·Make·the·process·a·new·session·leader.·This·detaches·it·from·the |
| 117 | ····//·terminal. | 116 | ····//·terminal. |
| 118 | ····setsid(); | 117 | ····setsid(); |
| 119 | | 118 | |
| 120 | ····//·A·process·inherits·its·working·directory·from·its·parent.·This·could·be | 119 | ····//·A·process·inherits·its·working·directory·from·its·parent.·This·could·be |
| 121 | ····//·on·a·mounted·filesystem,·which·means·that·the·running·daemon·would | 120 | ····//·on·a·mounted·filesystem,·which·means·that·the·running·daemon·would |
| 122 | ····//·prevent·this·filesystem·from·being·unmounted.·Changing·to·the·root | 121 | ····//·prevent·this·filesystem·from·being·unmounted.·Changing·to·the·root |
| 123 | ····//·directory·avoids·this·problem. | 122 | ····//·directory·avoids·this·problem. |
| 124 | ····chdir("/"); | 123 | ····chdir("/"); |
| 125 | | 124 | |
| 126 | ····//·The·file·mode·creation·mask·is·also·inherited·from·the·parent·process. | 125 | ····//·The·file·mode·creation·mask·is·also·inherited·from·the·parent·process. |
| 127 | ····//·We·don't·want·to·restrict·the·permissions·on·files·created·by·the | 126 | ····//·We·don't·want·to·restrict·the·permissions·on·files·created·by·the |
| 128 | ····//·daemon,·so·the·mask·is·cleared. | 127 | ····//·daemon,·so·the·mask·is·cleared. |
| 129 | ····umask(0); | 128 | ····umask(0); |
| 130 | | 129 | |
| 131 | ····//·A·second·fork·ensures·the·process·cannot·acquire·a·controlling·terminal. | 130 | ····//·A·second·fork·ensures·the·process·cannot·acquire·a·controlling·terminal. |
| 132 | ····if·(pid_t·pid·=·fork()) | 131 | ····if·(pid_t·pid·=·fork()) |
| 133 | ····{ | 132 | ····{ |
| 134 | ······if·(pid·>·0) | 133 | ······if·(pid·>·0) |
| 135 | ······{ | 134 | ······{ |
| 136 | ········exit(0); | 135 | ········exit(0); |
| 137 | ······} | 136 | ······} |
| 138 | ······else | 137 | ······else |
| 139 | ······{ | 138 | ······{ |
| 140 | ········syslog(LOG_ERR·|·LOG_USER,·"Second·fork·failed:·%m"); | 139 | ········syslog(LOG_ERR·|·LOG_USER,·"Second·fork·failed:·%m"); |
| 141 | ········return·1; | 140 | ········return·1; |
| 142 | ······} | 141 | ······} |
| 143 | ····} | 142 | ····} |
| 144 | | 143 | |
| 145 | ····//·Close·the·standard·streams.·This·decouples·the·daemon·from·the·terminal | 144 | ····//·Close·the·standard·streams.·This·decouples·the·daemon·from·the·terminal |
| 146 | ····//·that·started·it. | 145 | ····//·that·started·it. |
| 147 | ····close(0); | 146 | ····close(0); |
| 148 | ····close(1); | 147 | ····close(1); |
| 149 | ····close(2); | 148 | ····close(2); |
| 150 | | 149 | |
| 151 | ····//·We·don't·want·the·daemon·to·have·any·standard·input. | 150 | ····//·We·don't·want·the·daemon·to·have·any·standard·input. |
| 152 | ····if·(open("/dev/null",·O_RDONLY)·<·0) | 151 | ····if·(open("/dev/null",·O_RDONLY)·<·0) |
| 153 | ····{ | 152 | ····{ |
| 154 | ······syslog(LOG_ERR·|·LOG_USER,·"Unable·to·open·/dev/null:·%m"); | 153 | ······syslog(LOG_ERR·|·LOG_USER,·"Unable·to·open·/dev/null:·%m"); |
| 155 | ······return·1; | 154 | ······return·1; |
| 156 | ····} | 155 | ····} |
| 157 | | 156 | |
| 158 | ····//·Send·standard·output·to·a·log·file. | 157 | ····//·Send·standard·output·to·a·log·file. |
| 159 | ····const·char*·output·=·"/tmp/asio.daemon.out"; | 158 | ····const·char*·output·=·"/tmp/asio.daemon.out"; |
| 160 | ····const·int·flags·=·O_WRONLY·|·O_CREAT·|·O_APPEND; | 159 | ····const·int·flags·=·O_WRONLY·|·O_CREAT·|·O_APPEND; |
| 161 | ····const·mode_t·mode·=·S_IRUSR·|·S_IWUSR·|·S_IRGRP·|·S_IROTH; | 160 | ····const·mode_t·mode·=·S_IRUSR·|·S_IWUSR·|·S_IRGRP·|·S_IROTH; |
| 162 | ····if·(open(output,·flags,·mode)·<·0) | 161 | ····if·(open(output,·flags,·mode)·<·0) |
| 163 | ····{ | 162 | ····{ |
| 164 | ······syslog(LOG_ERR·|·LOG_USER,·"Unable·to·open·output·file·%s:·%m",·output); | 163 | ······syslog(LOG_ERR·|·LOG_USER,·"Unable·to·open·output·file·%s:·%m",·output); |
| 165 | ······return·1; | 164 | ······return·1; |
| 166 | ····} | 165 | ····} |
| 167 | | 166 | |
| 168 | ····//·Also·send·standard·error·to·the·same·log·file. | 167 | ····//·Also·send·standard·error·to·the·same·log·file. |
| 169 | ····if·(dup(1)·<·0) | 168 | ····if·(dup(1)·<·0) |
| 170 | ····{ | 169 | ····{ |
| 171 | ······syslog(LOG_ERR·|·LOG_USER,·"Unable·to·dup·output·descriptor:·%m"); | 170 | ······syslog(LOG_ERR·|·LOG_USER,·"Unable·to·dup·output·descriptor:·%m"); |
| 172 | ······return·1; | 171 | ······return·1; |
| 173 | ····} | 172 | ····} |
| 174 | | 173 | |
| 175 | ····//·Inform·the·io_context·that·we·have·finished·becoming·a·daemon.·The | 174 | ····//·Inform·the·io_context·that·we·have·finished·becoming·a·daemon.·The |
| 176 | ····//·io_context·uses·this·opportunity·to·create·any·internal·file·descriptors | 175 | ····//·io_context·uses·this·opportunity·to·create·any·internal·file·descriptors |
| 177 | ····//·that·need·to·be·private·to·the·new·process. | 176 | ····//·that·need·to·be·private·to·the·new·process. |
| 178 | ····io_context.notify_fork(asio::io_context::fork_child); | 177 | ····io_context.notify_fork(asio::io_context::fork_child); |
| 179 | | 178 | |
| 180 | ····//·The·io_context·can·now·be·used·normally. | 179 | ····//·The·io_context·can·now·be·used·normally. |
| 181 | ····syslog(LOG_INFO·|·LOG_USER,·"Daemon·started"); | 180 | ····syslog(LOG_INFO·|·LOG_USER,·"Daemon·started"); |
| 182 | ····io_context.run(); | 181 | ····io_context.run(); |
| 183 | ····syslog(LOG_INFO·|·LOG_USER,·"Daemon·stopped"); | 182 | ····syslog(LOG_INFO·|·LOG_USER,·"Daemon·stopped"); |
| 184 | ··} | 183 | ··} |
| 185 | ··catch·(std::exception&·e) | 184 | ··catch·(std::exception&·e) |
| 186 | ··{ | 185 | ··{ |
| 187 | ····syslog(LOG_ERR·|·LOG_USER,·"Exception:·%s",·e.what()); | 186 | ····syslog(LOG_ERR·|·LOG_USER,·"Exception:·%s",·e.what()); |
| 188 | ····std::cerr·<<·"Exception:·"·<<·e.what()·<<·std::endl; | 187 | ····std::cerr·<<·"Exception:·"·<<·e.what()·<<·std::endl; |
| 189 | ··} | 188 | ··} |
| 190 | } | 189 | } |