-- UNIX Domain Sockets Example
-- So we can detect that child died.
died = false
function OnSigchld(sig)
died = true
unix.wait() -- Prevent it from becoming a zombie
end
assert(unix.sigaction(unix.SIGCHLD, OnSigchld))
-- So keyboard interurpts only go to subprocess.
oldint = assert(unix.sigaction(unix.SIGINT, unix.SIG_IGN))
oldquit = assert(unix.sigaction(unix.SIGQUIT, unix.SIG_IGN))
-- UNIX domain sockets need a file
tmpdir = os.getenv('TMPDIR') or '/tmp'
unixpath = '%s/redbean-unix.sock.%d' % {tmpdir, unix.getpid()}
-- Create child process which is the server.
child = assert(unix.fork())
if child == 0 then
server = assert(unix.socket(unix.AF_UNIX, unix.SOCK_STREAM))
assert(unix.setsockopt(server, unix.SOL_SOCKET, unix.SO_RCVTIMEO, 2))
assert(unix.bind(server, unixpath))
assert(unix.listen(server))
client = assert(unix.accept(server))
data = assert(unix.read(client))
assert(data == 'ping!')
assert(assert(unix.write(client, 'pong!')) == 5)
assert(unix.close(client))
unix.exit(0)
end
-- Wait for the child to create the the socket file.
function FileExists(path)
st, err = unix.stat(path)
return not err
end
expobackoff = 1
while not died do
if FileExists(unixpath) then
break
else
expobackoff = expobackoff << 1
unix.nanosleep(expobackoff // 1000000000,
expobackoff % 1000000000)
end
end
-- Now connect to the socket.
if not died then
client = assert(unix.socket(unix.AF_UNIX, unix.SOCK_STREAM))
assert(unix.connect(client, unixpath))
assert(assert(unix.write(client, 'ping!')) == 5)
data = assert(unix.read(client))
assert(data == 'pong!')
itworked = true
else
itworked = false
end
-- Wait for client to terminate. We don't check error here because if
-- the child already died and the signal handler reaped it, then this
-- returns a ECHILD error which is fine.
unix.wait()
assert(itworked)
-- Now clean up the socket file.
unix.unlink(unixpath)
SetStatus(200)
SetHeader('Connection', 'close') -- be lazy and let _Exit() clean up signal handlers
SetHeader('Content-Type', 'text/html; charset=utf-8')
Write('<!doctype html>\r\n')
Write('<title>redbean unix domain sockets example</title>\r\n')
Write('<h1>\r\n')
Write('<img style="vertical-align:middle" src="data:image/png;base64,\r\n')
Write(EncodeBase64(LoadAsset('/redbean.png')))
Write('">\r\n')
Write('redbean unix domain sockets example\r\n')
Write('</h1>\r\n')
Write([[
<p>
<strong>It worked!</strong> We successfully sent a ping
pong via UNIX local sockets. Please check out the source
code to this example inside your redbean at unix-unix.lua.
</p>
]])
Write('</h1>\r\n')