Assume a system that contains only the basic Perl installation without any extra CPAN modules (LWP is hence NOT installed). Some of my target environments have limited space and I cannot increase my footprint at all (otherwise I would use LWP).
What is the most portable and reliable way to issue a HTTP POST request from such a system, and then retrieve the response?
HTTP::Lite is pure-Perl, so you can just bundle it along with your existing code.
Consider this. HTTP POSTs are not trivial. You need to assemble the data into a MIME blob, encode it properly, then open a Socket connection, send the data, then read any response headers from the socket to make sure it worked.
You'll be doing a lot of work to duplicate what LWP already does, and then you'll take all that work and put it in your environment that doesn't have LWP.
At that point, you will ask yourself, "gee, if I can put my own Perl code on this environment, why can't I just put LWP there?"
Never fear, for I am here to save you three months of useless work.
How to install Perl modules locally
If you can't do that, then
How to use PAR to package and distribute dependencies
Good luck, and don't duplicate code.
I just do HTTP Post like this without using any library,
sub post {
local($host,$port,$request,$data) = @_;
($fqdn, $aliases, $type, $len, $thataddr) = gethostbyname($host);
$that = pack($sockaddr, &AF_INET, $port, $thataddr);
socket(FS, &AF_INET, &SOCK_STREAM, $proto) || return undef;
bind(FS, $thissock) || return undef;
local($/);
unless (eval q!
$SIG{'ALRM'} = "timeout";
alarm($timeout);
connect(FS, $that) || return undef;
select(FS); $| = 1; select(STDOUT);
print FS "POST $request HTTP/1.0\r\n$referer";
print FS "$useragent";
print FS "Host: $host:$port\r\n$mimeaccept";
print FS "$cnt_type";
$len = length($data);
print FS "Content-length: $len\r\n\r\n$data\r\n";
undef($page);
$/ = "\n";
$_ = <FS>;
if (m:HTTP/1.0\s+\d+\s+:) { #HTTP/1.0
while(<FS>) {
last if /^[\r\n]+$/; # end of header
}
undef($/);
$page = <FS>;
}
else { # old style server reply
undef($/);
$page = $_;
$_ = <FS>;
$page .= $_;
}
$SIG{'ALRM'} = "IGNORE";
!) {
return undef;
}
close(FS);
$page;
}
I use this with a real old server (first generation Apache httpd). It doesn't support HTTP/1.1, chunked encoding etc but you get the idea.
See if there are any other programs available that you could call to perform the post. curl, wget, lynx, or Java for example.
HTTP POST is really trivial if you only want to post plain text, which should suffice for most applications.
I use this code which requires only IO::Socket (running on my NAS with perl 5.8.8) to post sensor data (acquired on my LAN via UDP, also via another IO::Socket) to an influxdb server on the internet:
my $REMOTE = new IO::Socket::INET (PeerAddr => 'yourhostname.com', PeerPort => '8086',
Proto => 'tcp', Timeout => '1', Blocking => '0')
or die "can't connect - connection busy?";
$REMOTE->autoflush(1);
my $data = "POOL ph=$ph,orp=$orp";
my $len = length($data);
print $REMOTE "POST /write?db=esp-sensors HTTP/1.1\n",
"Host: yourhostname.com\n",
"Connection: close\n",
"Content-Type: application/x-www-form-urlencoded\n",
"Content-Length: $len\n\n",
"$data\n";
close($REMOTE);
Granted, I don't check the result. But I assume it would be possible. Since there is nothing I could do about any failure anyway, I don't care if it fails, someday I'll see data missing in the graph and check whats up.