Socket Connection

Overview

The Socket Connection module allows an application to transmit data over a socket connection through the TCP, UDP, or TLS protocol.

Basic Concepts

• Socket: An abstraction of endpoints for bidirectional communication between application processes running on different hosts in a network.
• TCP: Transmission Control Protocol, which is a byte stream–based transport layer communication protocol that is connection-oriented and reliable.
• UDP: User Datagram Protocol, which is a simple datagram-oriented transport layer communication protocol.
• TLS: Transport Layer Security, which is a protocol that ensures the data confidentiality and integrity between communication programs.

When to Use

Applications transmit data over TCP, UDP, or TLS socket connections. The main application scenarios are as follows:

• Implementing data transmission over TCP socket or UDP socket connections
• Implementing data transmission over TCP socket server connections
• Implementing encrypted data transmission over TLS socket connections

Available APIs

For the complete list of APIs and example code, see Socket Connection.

Socket connection functions are mainly implemented by the socket module. The following table describes the related APIs.

TLS socket connection functions are mainly provided by the tls_socket module. The following table describes the related APIs.

Transmitting Data over TCP Socket or UDP Socket Connections

The implementation is similar for UDP socket and TCP socket connections. The following uses data transmission over a TCP socket connection as an example.

1. Import the required socket module.

2. Create a TCP socket connection. A TCPSocket object is returned.

3. (Optional) Subscribe to TCP socket connection events.

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

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

6. Send data over the connection.

7. Enable the TCP socket connection to be automatically closed after use.

import socket from '@ohos.net.socket';
import { BusinessError } from '@ohos.base';

class SocketInfo {
  message: ArrayBuffer = new ArrayBuffer(1);
  remoteInfo: socket.SocketRemoteInfo = {} as socket.SocketRemoteInfo;
}
// Create a TCP socket connection. A TCPSocket object is returned.
let tcp = socket.constructTCPSocketInstance();
tcp.on('message', (value: SocketInfo) => {
  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 local IP address and port number.
let ipAddress : socket.NetAddress = {} as socket.NetAddress;
ipAddress.address = "192.168.xxx.xxx";
ipAddress.port = 1234;
tcp.bind(ipAddress, (err: BusinessError) => {
  if (err) {
    console.log('bind fail');
    return;
  }
  console.log('bind success');

  // Set up a connection to the specified IP address and port number.
  ipAddress.address = "192.168.xxx.xxx";
  ipAddress.port = 5678;

  let tcpConnect : socket.TCPConnectOptions = {} as socket.TCPConnectOptions;
  tcpConnect.address = ipAddress;
  tcpConnect.timeout = 6000;

  tcp.connect(tcpConnect, (err: BusinessError) => {
    if (err) {
      console.log('connect fail');
      return;
    }
    console.log('connect success');
    // Send data over the connection.
    let tcpSendOptions : socket.TCPSendOptions = {} as socket.TCPSendOptions;
    tcpSendOptions.data = 'Hello, server!';
    tcp.send(tcpSendOptions, (err: BusinessError) => {
      if (err) {
        console.log('send fail');
        return;
      }
      console.log('send success');
    })
  });
});

// Enable the socket connection to be automatically closed after use. Then, unsubscribe from events of the connection.
setTimeout(() => {
  tcp.close((err: BusinessError) => {
    console.log('close socket.');
  });
  tcp.off('message');
  tcp.off('connect');
  tcp.off('close');
}, 30 * 1000);

Transmitting Data over TCP Socket Server Connections

How to Develop

The TCP socket server connection process is described as follows:

1. Import the required socket module.
2. Create a TCP socket server connection. A TCPSocketServer object is returned.
3. Bind the local IP address and port, and listen for and accept TCP socket connections established over the socket.
4. Subscribe to connect events of the TCPSocketServer object to listen for client connection status changes.
5. Set up a connection between the client and the server. A TCPSocketConnection object is returned.
6. Subscribe to events of the TCPSocketConnection object, and send data to the client through the TCPSocketConnection object.
7. Close the connection between the client and the server.
8. Unsubscribe from events of the TCPSocketConnection and TCPSocketServer objects.

import socket from '@ohos.net.socket';
import { BusinessError } from '@ohos.base';
// Create a TCP socket server connection. A TCPSocketServer object is returned.
let tcpServer = socket.constructTCPSocketServerInstance();
// Bind the local IP address and port number for listening.

let ipAddress : socket.NetAddress = {} as socket.NetAddress;
ipAddress.address = "192.168.xxx.xxx";
ipAddress.port = 4651;
tcpServer.listen(ipAddress, (err: BusinessError) => {
  if (err) {
    console.log("listen fail");
    return;
  }
  console.log("listen success");
});

class SocketInfo {
  message: ArrayBuffer = new ArrayBuffer(1);
  remoteInfo: socket.SocketRemoteInfo = {} as socket.SocketRemoteInfo;
}
// Subscribe to connect events of the TCPSocketServer object.
tcpServer.on("connect", (client: socket.TCPSocketConnection) => {
  // Subscribe to events of the TCPSocketConnection object.
  client.on("close", () => {
    console.log("on close success");
  });
  client.on("message", (value: SocketInfo) => {
    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("received message--:" + str);
    console.log("received address--:" + value.remoteInfo.address);
    console.log("received family--:" + value.remoteInfo.family);
    console.log("received port--:" + value.remoteInfo.port);
    console.log("received size--:" + value.remoteInfo.size);
  });

  // Send data to the client.
  let tcpSendOptions : socket.TCPSendOptions = {} as socket.TCPSendOptions;
  tcpSendOptions.data = 'Hello, client!';
  client.send(tcpSendOptions, (err: BusinessError) => {
    if (err) {
      console.log("send fail");
      return;
    }
    console.log("send success");
  });

  // Close the connection between the client and the server.
  client.close((err: BusinessError) => {
    if (err) {
      console.log("close fail");
      return;
    }
    console.log("close success");
  });

  // Unsubscribe from events of the TCPSocketConnection object.
  setTimeout(() => {
    client.off("message");
    client.off("close");
  }, 10 * 1000);
});

// Unsubscribe from events of the TCPSocketServer object.
setTimeout(() => {
  tcpServer.off("connect");
}, 30 * 1000);

Implementing Encrypted Data Transmission over TLS Socket Connections

How to Develop

The TLS socket connection process on the client is described as follows:

1. Import the required socket module.

2. Bind the IP address and port number of the server.

3. For two-way authentication, upload the client CA certificate and digital certificate. For one-way authentication, upload the client CA certificate.

4. Create a TLS socket connection. A TLSsocket object is returned.

5. (Optional) Subscribe to TLS socket connection events.

6. Send data over the connection.

7. Enable the TLS socket connection to be automatically closed after use.

import socket from '@ohos.net.socket';
import { BusinessError } from '@ohos.base';

class SocketInfo {
  message: ArrayBuffer = new ArrayBuffer(1);
  remoteInfo: socket.SocketRemoteInfo = {} as socket.SocketRemoteInfo;
}
// Create a TLS socket connection (for two-way authentication). A TLSSocket object is returned.
let tlsTwoWay = socket.constructTLSSocketInstance();
// Subscribe to TLS socket connection events.
tlsTwoWay.on('message', (value: SocketInfo) => {
  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);
});
tlsTwoWay.on('connect', () => {
  console.log("on connect");
});
tlsTwoWay.on('close', () => {
  console.log("on close");
});

// Bind the local IP address and port number.
let ipAddress : socket.NetAddress = {} as socket.NetAddress;
ipAddress.address = "192.168.xxx.xxx";
ipAddress.port = 4512;
tlsTwoWay.bind(ipAddress, (err: BusinessError) => {
  if (err) {
    console.log('bind fail');
    return;
  }
  console.log('bind success');
});

ipAddress.address = "192.168.xxx.xxx";
ipAddress.port = 1234;

let tlsSecureOption : socket.TLSSecureOptions = {} as socket.TLSSecureOptions;
tlsSecureOption.key = "xxxx";
tlsSecureOption.cert = "xxxx";
tlsSecureOption.ca = ["xxxx"];
tlsSecureOption.password = "xxxx";
tlsSecureOption.protocols = [socket.Protocol.TLSv12];
tlsSecureOption.useRemoteCipherPrefer = true;
tlsSecureOption.signatureAlgorithms = "rsa_pss_rsae_sha256:ECDSA+SHA256";
tlsSecureOption.cipherSuite = "AES256-SHA256";

let tlsTwoWayConnectOption : socket.TLSConnectOptions = {} as socket.TLSConnectOptions;
tlsSecureOption.key = "xxxx";
tlsTwoWayConnectOption.address = ipAddress;
tlsTwoWayConnectOption.secureOptions = tlsSecureOption;
tlsTwoWayConnectOption.ALPNProtocols = ["spdy/1", "http/1.1"];

// Set up a connection.
tlsTwoWay.connect(tlsTwoWayConnectOption, () => {
  console.error("connect function");
});

// Enable the socket connection to be automatically closed after use. Then, unsubscribe from events of the connection.
tlsTwoWay.close((err: BusinessError) => {
  if (err) {
    console.log("close callback error = " + err);
  } else {
    console.log("close success");
  }
  tlsTwoWay.off('message');
  tlsTwoWay.off('connect');
  tlsTwoWay.off('close');
});

// Create a TLS socket connection (for one-way authentication). A TLSsocket object is returned.
let tlsOneWay = socket.constructTLSSocketInstance(); // One way authentication

// Subscribe to TLS socket connection events.
tlsTwoWay.on('message', (value: SocketInfo) => {
  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);
});
tlsTwoWay.on('connect', () => {
  console.log("on connect");
});
tlsTwoWay.on('close', () => {
  console.log("on close");
});

// Bind the local IP address and port number.
ipAddress.address = "192.168.xxx.xxx";
ipAddress.port = 5445;
tlsOneWay.bind(ipAddress, (err:BusinessError) => {
  if (err) {
    console.log('bind fail');
    return;
  }
  console.log('bind success');
});

ipAddress.address = "192.168.xxx.xxx";
ipAddress.port = 8789;
let tlsOneWaySecureOption : socket.TLSSecureOptions = {} as socket.TLSSecureOptions;
tlsOneWaySecureOption.ca = ["xxxx", "xxxx"];
tlsOneWaySecureOption.cipherSuite = "AES256-SHA256";

let tlsOneWayConnectOptions: socket.TLSConnectOptions = {} as socket.TLSConnectOptions;
tlsOneWayConnectOptions.address = ipAddress;
tlsOneWayConnectOptions.secureOptions = tlsOneWaySecureOption;

// Set up a connection.
tlsOneWay.connect(tlsOneWayConnectOptions, () => {
  console.error("connect function");
});

// Enable the socket connection to be automatically closed after use. Then, unsubscribe from events of the connection.
tlsTwoWay.close((err: BusinessError) => {
  if (err) {
    console.log("close callback error = " + err);
  } else {
    console.log("close success");
  }
  tlsTwoWay.off('message');
  tlsTwoWay.off('connect');
  tlsTwoWay.off('close');
});