- Socket: How a client application works
- Step 1: Connecting to the server
- Step 2: Exchanging data
- Step 3: Ending the communication
- Transmission mode of information
Socket: Creating a client application
A client application of a socket server connects to a standard server to exchange information via a socket.
Example: A client WINDEV application can connect to a standard news server on Internet.
Socket: How a client application works
Step 1: Connecting to the server
To connect to a server socket, all you have to do is use SocketConnect
. This function makes a connection request to the server.
The socket is identified by its port and address.
Step 2: Exchanging data
Once two machines have connected their sockets, a communication channel is established between them. These two machines can read from and write character strings to the socket.
Remark: To avoid locking the applications, the management of incoming messages is often performed by a specific thread (for more details, see Managing threads
To read from and write to the socket of the server, the WINDEV client application must use SocketRead
Caution: To start a read operation, a write operation must have been done previously. For example:
- The client machine writes to the socket: it sends a request to the server.
- The server computer performs a read operation in the socket.
- If a response to the message is required, the server sends a response to the client computer.
Step 3: Ending the communication
To end the communication, close the socket from the client machine with SocketClose
Remark: you also have the ability to end the communication from the server.
Transmission mode of information
The transmission mode of the message defines the mode used to specify the length of the message.
Several methods are available to find out the length of message during the communication between sockets.
Method 1: WINDEV mode: By default, the number of characters in the message is specified at the beginning of message. This transmission mode is recommended when the sockets are used to communicate between two WINDEV applications.
The message has the following format: "11\r\nHelloWorld"
Method 2: standard mode: The end of the message is signaled by a specific character, defined in advance. This transmission mode is recommended when the sockets are used to communicate between a WINDEV application and another application. In this case, a specific character must be included in the message to indicate that the message is over.
The message has the following format: "Hello World<EOF>"
Method 3: standard mode with buffer
: Corresponds to the standard mode optimized for the most frequently used protocols on Internet.
allows you to modify the transmission mode used.
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