NETWORK PROGRAMMING WITH PERL PDF
Programming the Network with Perl · Read more Programming the Perl DBI: Database Programming with Perl. Read more. PDF - Network Programming with Perl. "Network programming"--the term had a distinct meaning once, but now it begs the question, "Is there another kind?. PERL - SOCKET PROGRAMMING. What is a Socket? Socket is a Berkeley UNIX mechanism of creating a virtual duplex connection between different processes.
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appropriate Perl packages. For example, Chapter 13, Networking: Implementing RPC, explains the implementation of an RPC toolkit that avoids deadlocks even. and Perl Scripting for Network Operators We'll introduce shell and Perl syntax and concepts Portable Shell Programming, Blinn - Prentice Hall. • Classic. Networking with Perl. Sockets r. Clients and Servers. The Server Side of a Conversation s. The Client Side of a Conversation s r. Some Network Examples.
Our first programming example is a simple server running on one machine that can service only one client program at a time connecting from the same or a different machine.
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Recall that the steps for creating a server were to create a socket, bind it to a port, listen at the port and accept client connections. Listing 1, server1. First, it is generally a good idea to compile using Perl's strict rules: use strict; This requires all variables to be declared with the my function before they are used. Using my may be inconvenient, but it can catch many common syntactically correct yet logically incorrect programming bugs.
When choosing a port for your server, pick one that is unused on your machine.
Note that the only way to ensure you select a port that does not have a predefined use is to look at the appropriate RFC see Resources. Next, the socket is created using the socket function. A socket is like a file handle—it can be read from, written to or both. The function setsockopt is called to ensure that the port will be immediately reusable. Then, the listen function causes the server to begin listening at the port.
The second argument to the listen function is the maximum queue length or the maximum number of pending client connections. Once the server begins listening at the port, it can accept client connections using the accept function. Reading from the socket reads the client's output and printing to the socket sends data to the client.
To write to it, use the print function: print SOCKET; The return value of the accept function is the Internet address of the client in a packed format. To convert the packed numeric address to a host name, the function gethostbyaddr is used. Let's assume all of the servers referred to in this article are started on the machine named server. A Simple Client Listing 2. Listing 2, client1. The first command-line argument to this program is the host name to which it should connect, which defaults to server.
The second command-line argument is the port number which defaults to A socket is then created using socket and the client connects the socket to the port address using connect. The while loop then reads the data the server sends to the client until the end-of-file is reached, printing this input to STDOUT. Then the socket is closed. Let's assume all of the clients are started on the the machine named client.
But using the functions above is too hard; I prefer the easy way—IO::Socket. The module IO::Socket provides an easy way to create sockets which can then be used like file handles. If you don't have it installed on your machine, it can be found on CPAN.
Listing 3, serverIO.
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Note that the arguments to the method include the host name, port number, protocol, queue length and an option indicating we want this port to be immediately reusable.
This socket can be used like a file handle—we can either read the client output from it, or write to it by sending data to the client. A client connection is accepted using the accept method. Then the socket associated with that client is read until end-of-file. Listing 4, clientIO. This time, a new object is created that connects to a host at a port using the TCP protocol. Ten strings are then printed to that server, then the socket is closed. If the server in Listing 3, serverIO. For instance, the client may send information to the server, then the server may send information back to the client.
Therefore, network programs can be written so that the server and client follow some predetermined protocol. Listing 5. Listing 5, server2way.
The module Sys::Hostname provides a function named hostname that returns the host name of the server. Then a while loop is executed that accepts connections. When a client connects, the server reads a line from the client, chopping off the newline character.
Then a switch statement is executed. The switch is cleverly disguised as a foreach loop, which happens to be one of my favorite ways of writing a switch. Depending on the input entered by the client, the server outputs an appropriate response. All lines from the client are read until end-of-file.
PDF - Network Programming with Perl
Listing 6, client2way. A connection to the server is made, then the client prints a few commands to the server reads the response and prints the response to STDOUT. A solution can be written using select that does not fork, but it is more complicated.
The client's parent process will read the commands from the user through STDIN and print them to the server. Listing 7. Listing 7, clientfork. To fork in Perl, call the cleverly named fork function. It returns undef if the fork fails.
If it succeeds, it returns 0 to the child, non-zero the child's pid to the parent. In clientfork. The following is the example session executing the client code in Listing 7, clientfork. It is very important the parent reap its child so that the child does not outlive the parent and become a zombie.
A Forking Server Listing 8. Servers usually don't handle only one client at a time. One approach to a server that can handle more than one client is a server that forks a child process to handle each client connection. Listing 8, serverfork. Within the while loop that accepts all the client connections, the server forks. If the fork returns true, the parent is running and it executes the next statement which immediately transfers control to the continue block, performs the housecleaning step of closing the child socket and waits for the next client to connect.
If the fork returns undef, then the fork failed, so the server dies. If the fork returns neither true nor undef, then the child is running, so the parent socket is closed and the child reads from the client and processes the client.
When the child is finished processing the client, the child exits and is reaped by the parent. Thread Programming in Perl5. This means a threaded networking program can be created to be either a server or a client.
Listings 9, 10, and 11 are three different versions of a client that logs into several web servers and determines the type of server being used Apache, Netscape, etc. Listing 9. How does it work in Perl? Socket is called Port which sends and receives data over a network.
How does it work in Perl?
This was later ported on to every known OS that enables to communicate between systems across geographical locations that run on different OS software. If this would not have happened most of the communication would never ever happen between systems over the network.
Taking more closure look point of view; a typical computer system on a network receives and sends information as desired by the various applications running on it. This information is routed to the system, which is called a socket, since a unique IP address is designated to it.
On the system, this information is given to the relevant applications, which later listen on different ports. For example an internet browser listens on port 80 for information that is received from the web server. For now, let's assume that a socket is an IP address and a port, enabling connection to send and receive data over a network. To explain above mentioned socket concept we will take an example of Client - Server Programming using Perl.
Bind the socket to a port address using bind call. Listen to the socket at the port address using listen call. Accept client connections using accept call. To Create a Client Create a socket with socket call. Connect the socket to the server using connect call.Client Side Socket Calls The connect call If the user wants to prepare client program, then first you will use socket call to create a socket and then use connect call to connect to the server. Archive the directory using tar.
Let's see how it has been done, assuming to have both server and client on the same machine. Listing 1, server1. The protocol chosen is tcp the choices are tcp, udp and icmp; the default is udp. A Simple Client Listing 2. If this would not have happened most of the communication would never ever happen between systems over the network.
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