In this module, we will explore how to use Control Language (CL) to handle network communication. This includes understanding the basics of network protocols, sending and receiving data over a network, and integrating network communication into your CL programs.

By the end of this module, you will:

• Understand the basics of network communication.
• Learn how to send and receive data over a network using CL.
• Integrate network communication into your CL programs.

Network communication involves the exchange of data between devices over a network. This can include local area networks (LANs), wide area networks (WANs), and the internet.

• Protocols: Rules that define how data is transmitted and received over a network (e.g., TCP/IP, HTTP, FTP).
• Sockets: Endpoints for sending and receiving data.
• Ports: Logical channels through which data is sent and received.

To send data over a network using TCP/IP in CL, you can use the SNDSRVTBLE command. This command sends data to a specified IP address and port.

• DCL VAR(&DATA) TYPE(*CHAR) LEN(100): Declares a variable to hold the data to be sent.
• DCL VAR(&IPADDR) TYPE(*CHAR) LEN(15) VALUE('192.168.1.100'): Declares a variable for the IP address of the server.
• DCL VAR(&PORT) TYPE(*DEC) LEN(5 0) VALUE(8080): Declares a variable for the port number.
• CHGVAR VAR(&DATA) VALUE('Hello, this is a test message.'): Assigns a value to the data variable.
• SNDSRVTBLE DATA(&DATA) IPADDR(&IPADDR) PORT(&PORT): Sends the data to the specified IP address and port.

To receive data over a network using TCP/IP in CL, you can use the RCVSRVTBLE command. This command listens for incoming data on a specified port.

• DCL VAR(&DATA) TYPE(*CHAR) LEN(100): Declares a variable to hold the received data.
• DCL VAR(&PORT) TYPE(*DEC) LEN(5 0) VALUE(8080): Declares a variable for the port number.
• RCVSRVTBLE DATA(&DATA) PORT(&PORT): Listens for incoming data on the specified port and stores it in the data variable.
• SNDPGMMSG MSG(&DATA): Sends a program message with the received data.

Let's create a simple chat application where one CL program sends messages and another receives them.

Sender Program

Receiver Program

• The sender program sends a chat message to the specified IP address and port.
• The receiver program listens for incoming messages on the specified port and displays them.

Modify the sender program to allow the user to input the message to be sent.

Solution

Add error handling to the receiver program to handle cases where no data is received.

Solution

In this module, we covered the basics of network communication in CL, including sending and receiving data over a network. We also integrated network communication into CL programs with practical examples and exercises. Understanding these concepts will enable you to create more dynamic and interactive CL programs that can communicate over a network.