Socket Connection

Use Cases

Your application can transmit data through Socket connections. Currently, the TCP and UDP protocols are supported.

Available APIs

The Socket connection function is mainly implemented by the Socket module. The following table describes the related APIs.

API Description
constructUDPSocketInstance() Creates a UDPSocket object.
constructTCPSocketInstance() Creates a TCPSocket object.
bind() Binds the IP address and port number.
send() Sends data.
close() Closes a Socket connection.
getState() Obtains the Socket connection status.
connect() Connects to the specified IP address and port. This function is supported only for TCP.
getRemoteAddress() Obtains the peer address of the Socket connection. This function is supported only for TCP. The connect API must have been called before you use this API.
on(type: 'message') Enables listening for message events of the Socket connection.
off(type: 'message') Disables listening for message events of the Socket connection.
on(type: 'close') Enables listening for close events of the Socket connection.
off(type: 'close') Disables listening for close events of the Socket connection.
on(type: 'error') Enables listening for error events of the Socket connection.
off(type: 'error') Disables listening for error events of the Socket connection.
on(type: 'listening') Enables listening for listening events of the UDPSocket connection.
off(type: 'listening') Disables listening for listening events of the UDPSocket connection.
on(type: 'connect') Enables listening for connect events of the TCPSocket connection.
off(type: 'connect') Disables listening for connect events of the TCPSocket connection.

How to Develop

The implementation is similar for UDPSocket and TCPSocket. The following uses the TCPSocket as an example.

  1. Import the required Socket module.

  2. Create a TCPSocket object.

  3. (Optional) Enable listening for TCPSocket events.

  4. Bind the IP address and port number. The port number can be specified or randomly allocated by the system.

  5. Set up a connection to the specified IP address and port number.

  6. Send data.

  7. Enable the TCPSocket connection to be automatically closed after use.

    import socket from '@ohos.net.socket'

// Create a TCPSocket object.
let tcp = socket.constructTCPSocketInstance();

// Enable listening for TCPSocket events.
tcp.on('message', value => {
    console.log("on message")
    let buffer = value.message
    let dataView = new DataView(buffer)
    let str = ""
    for (let i = 0;i < dataView.byteLength; ++i) {
        str += String.fromCharCode(dataView.getUint8(i))
    }
    console.log("on connect received:" + str)
});
tcp.on('connect', () => {
    console.log("on connect")
});
tcp.on('close', () => {
    console.log("on close")
});

// Bind the IP address and port number.
let bindAddress = {
    address: '192.168.xx.xx',
    port: 1234, // Bound port, for example, 1234.
    family: 1
};
tcp.bind(bindAddress, err => {
    if (err) {
        console.log('bind fail');
        return;
    }
    console.log('bind success');
    // Set up a connection to the specified IP address and port number.
    let connectAddress = {
        address: '192.168.xx.xx',
        port: 5678, // Connection port, for example, 5678.
        family: 1
    };
    tcp.connect({
        address: connectAddress, timeout: 6000
    }, err => {
        if (err) {
            console.log('connect fail');
            return;
        }
        console.log('connect success');
        // Send data.
        tcp.send({
            data: 'Hello, server!'
        }, err => {
            if (err) {
                console.log('send fail');
                return;
            }
            console.log('send success');
        })
    });
});
// Enable the TCPSocket connection to be automatically closed after use. Then, disable listening for TCPSocket events.
setTimeout(() => {
    tcp.close((err) => {
        console.log('close socket.')
    });
    tcp.off('message');
    tcp.off('connect');
    tcp.off('close');
}, 30 * 1000);