Author: Armel Fauveau
Original address: http://www.phpbuilder.net/columns/armel20010427.php3
Translator: Xu [email protected]
Http://www.phpobject.net/blog/
PHP can open sockets of remote or local servers! Here is a simple example using sockets: connect to a Usenet news server, communicate with the server, and download some articles from a precise news group.
Open Socket using PHP
Use fsockopen() to open a Socket. This function exists in both PHP3 and PHP4. The prototype of the function is as follows:
<?php
intfsockopen
(string hostname,
int port[,
int errno[,
string errstr[,
double timeout]]])
?>
For network hosts, it will establish a TCP Socket connection to the port of the hostname. The hostname can be a domain name or an IP address. For UDP connections, you need to specify the protocol: udp://hostname. For unix hosts, the hostname will be used in the path to the socket, and the port must be set to 0 in this example. The optional timeout can be used to set the number of seconds for connection timeout.
More information about fsockopen() can be found at http://www.php.net/manual/function.fsockopen.php
Network News Transfer Protocol (NNTP)
Accessing a usenet news server requires the use of a special protocol called NNTP, the Network News Transfer Protocol standard. The details of this protocol are in RFC977, which you can view at http://www.w3.org/Protocols/rfc977/rfc977.html . This document describes in detail how to use different commands to connect and talk to an NNTP server.
Connection Server Connecting to an NNTP server requires knowing the server's hostname (or IP address) and the port it will listen on. It is also recommended that you add a timeout so that the program will not "freeze" when the connection fails.
<?php
$cfgServer="your.news.host";
$cfgPort =119;
$cfgTimeOut =10;
// open asocket
if(!$cfgTimeOut)
// without timeout
$usenet_handle=fsockopen($cfgServer,$cfgPort);
else
// with timeout
$usenet_handle=fsockopen($cfgServer,$cfgPort, &$errno, &$errstr,$cfgTimeOut);
if(!$usenet_handle) {
echo"Connexionfailedn";
exit();
}
else {
echo"Connectedn";
$tmp=fgets($usenet_handle,1024);
}
?>
Interacting with the Server Now we are connected to the server and can interact with the server through the previously opened socket connection. Let's say to the server "We want to get the latest 10 articles from a certain news group". RFC977 defines the command on how to select the correct news grouping, as follows:
GROUPggg
The required parameter ggg is the name of the news group you want to select, such as net.news. Using the list command you can get a valid news list. A successful selection response will return the news numbers of the first and last two news articles in the group and an estimate of the archived news numbers.
for example
chrome:~$ telnetmy.news.host 119
Trying aa.bb.cc.dd...
Connected tomy.news.host.
Escape character is'^]'.
200 my.news.hostInterNetNews NNRP server INN 2.2.2 13-Dec-1999 ready (posting ok).
GROUP alt.test
211 232 222996 223235alt.test
quit
205.
After receiving the command "GROUP alt.test", the news server returned "211232 222996 223235 alt.test". 211 is the RFC identification code (a simple explanation that the command has been successfully executed - check RFC for more detailed information). The returned information indicates that there are 232 articles, among which the index number of the oldest news is 222996, and the latest The news index number is 223235. Now let's do the math: 222996+232 is not equal to 232235. The missing article was either removed from the server, canceled by its author (yes, it's possible and easy to do), or deleted.
As a precaution, the server may require authentication before selecting a news group, depending on whether the server is public or private. Generally, anyone is allowed to obtain news, but publishing news requires certification.
<?php
//$cfgUser = "xxxxxx";
//$cfgPasswd = "yyyyyy";
$cfgNewsGroup="alt.php";
// identification required on private server
if($cfgUser) {
fputs($usenet_handle,"AUTHINFO USER".$cfgUser."n");
$tmp=fgets($usenet_handle,1024);
fputs($usenet_handle,"AUTHINFOPASS".$cfgPasswd."n");
$tmp=fgets($usenet_handle,1024);
// check error
if($tmp!="281Okrn") {
echo "502Authentication errorn";
exit();
}
}
// select newsgroup
fputs($usenet_handle,"GROUP ".$cfgNewsGroup."n");
$tmp=fgets($usenet_handle,1024);
if($tmp=="480 Authentication required for commandrn") {
echo "$tmpn";
exit();
}
$info=split(" ",$tmp);
$first=$info[2];
$last=$info[3];
print"First : $firstn";
print"Last : $lastn";
?>
Get some articles Now that we have the A index number of the latest article, we can easily get the latest ten articles. RFC977 states that the ARTICLE command can be used with the article index number or message ID. For the sake of caution, here, the index number of the article and the message ID are different. Because each news server has different definitions, the index number of the same article on different news servers will be different, but the message ID should be unique. (Included in the header of the article)
<?php
$cfgLimit =10;
// upload last articles
$boucle=$last-$cfgLimit;
while ($boucle<=$last) {
set_time_limit(0);
fputs($usenet_handle,"ARTICLE$bouclen");
$article="";
$tmp=fgets($usenet_handle,4096);
if(substr($tmp,0,3) !="220") {
echo"+----------------------+n";
echo"Error onarticle $bouclen";
echo"+----------------------+n";
}
else {
while($tmp!=".rn") {
$tmp=fgets($usenet_handle,4096);
$article=$article.$tmp;
}
echo"+----------------------+n";
echo"Article$bouclen";
echo"+----------------------+n";
echo"$articlen";
}
$boucle++;
}
?>
We only get the ten latest news from this group on this server. You can also use the HEAD command to get the header information of the article, or the BODY command to get the body of the news.
Close the connection and use the fclose() function to end the session with the NNTP server. Of course, you can create a new file, as follows:
<?php
// close connexion
fclose($usenet_handle);
?>
For more information about fclose(), please see: http://www.php.net/manual/function.fclose.php
Conclusion In this article, we only showed how to open, use and close a socket connection under certain circumstances: connect to an NNTP server and retrieve some articles from the news group. Publishing an article on an NNTP server using the POST command is not much more complicated.
So the next step is to write a news client (and strip out some Netscape) that can easily save articles and index them using some search engine (such as htgid, http://www.htdig.org/) , and there must be a WEB application that can perform keyword searches under news groups. Here is an example, you can visit http://www.phpindex.com/ng/ to download it.