demo: launchd with inetdCompatibility

inet_wait.cxx

#include <arpa/inet.h>
#include <cstdlib>
#include <memory>
#include <syslog.h>
#include <thread>
#include <unistd.h>

int main()
{
    openlog("demod", LOG_PID, LOG_DAEMON);
    sockaddr_in sin;
    socklen_t socket_type_len = sizeof(sin);
    /* should be bound to stdin by inetd */
    if (getsockname(0, (sockaddr*)&sin, &socket_type_len)) {
        syslog(LOG_CRIT, "getsockname(): %s\n", strerror(errno));
        exit(-1);
    }
    syslog(LOG_INFO, "%s:%d \n", inet_ntoa(sin.sin_addr), ntohs(sin.sin_port));

    auto process = [](int fd, const sockaddr_in& peer) -> void {
        auto ptr = std::make_unique<char[]>(256);
        std::memset(ptr.get(), 0, 256);
        while (read(fd, ptr.get(), 255) > 0) {
            syslog(LOG_INFO, "fd %d (%s:%d): %s\n", fd, inet_ntoa(peer.sin_addr), ntohs(peer.sin_port), ptr.get());
        }
        close(fd);
    };
    while (true) {
        sockaddr_in clientaddr;
        socklen_t clientaddr_len = sizeof(clientaddr);
        auto accepted = accept(0, (sockaddr*)&clientaddr, &clientaddr_len);
        if (accepted < 0) {
            syslog(LOG_CRIT, "accept(): %s\n", strerror(errno));
            break;
        }
        syslog(LOG_INFO, "connected: %s:%d\n", inet_ntoa(clientaddr.sin_addr), ntohs(clientaddr.sin_port));
        std::thread th(process, accepted, clientaddr);
        th.detach();
    }
    closelog();
    return 0;
}

launchd_inet_wait.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>Label</key>
        <string>demo.launchd_socket_listener</string>
        <key>ProgramArguments</key>
        <array>
        <string>/Library/Application Support/socket_demo/launchd_inet_wait</string>
        </array>
        <key>Sockets</key>
        <dict>
                <key>Demo_SocketListerner</key>
                <dict>
            <key>SockPathName</key>
            <string>/tmp/demo_launchd_socket</string>
        </dict>
    </dict>
    <key>Sockets</key>
    <dict>
        <key>Listeners</key>
        <dict>
            <key>SockServiceName</key>
            <string>29980</string>
        </dict>
    </dict>
    <key>inetdCompatibility</key>
    <dict>
        <key>Wait</key>
        <true/>
    </dict>
</dict>
</plist>

demo for systemd user: systemd-socket-activate -l 29980 --inetd

and then try to connect localhost:29980 by netcat