Socket Connection

Introduction

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 TLSSocket connections. The main application scenarios are as follows:

• Implementing data transmission over TCP/UDPSocket connections
• Implementing encrypted data transmission over TLSSocket 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.

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

Transmitting Data over TCP/UDPSocket Connections

The implementation is similar for UDPSocket and TCPSocket connections. The following uses data transmission over a TCPSocket connection as an example.

1. Import the required socket module.

2. Create a TCPSocket object.

3. (Optional) Subscribe to TCPSocket connection 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();
   
   // Subscribe to TCPSocket connection 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 local 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 connection events.
   setTimeout(() => {
       tcp.close((err) => {
           console.log('close socket.')
       });
       tcp.off('message');
       tcp.off('connect');
       tcp.off('close');
   }, 30 * 1000);
   

Implementing encrypted data transmission over TLSSocket connections

How to Develop

TLSSocket connection process on the client:

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 TLSSocket object.

5. (Optional) Subscribe to TLSSocket connection events.

6. Send data.

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

// Create a TLSSocket connection (for two-way authentication).
let tlsTwoWay = socket.constructTLSSocketInstance();

// Subscribe to TLSSocket connection events.
tlsTwoWay.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)
});
tlsTwoWay.on('connect', () => {
  console.log("on connect")
});
tlsTwoWay.on('close', () => {
  console.log("on close")
});

// Bind the local IP address and port number.
tlsTwoWay.bind({address: '192.168.xxx.xxx', port: xxxx, family: 1}, err => {
  if (err) {
    console.log('bind fail');
    return;
  }
  console.log('bind success');
});

// Set the communication parameters.
let options = {
  ALPNProtocols: ["spdy/1", "http/1.1"],

  // Set up a connection to the specified IP address and port number.
  address: {
    address: "192.168.xx.xxx",
    port: xxxx, // Port
    family: 1,
  },

  // Set the parameters used for authentication during communication.
  secureOptions: {
    key: "xxxx",                            // Key
    cert: "xxxx",                           // Digital certificate
    ca: ["xxxx"],                           // CA certificate
    passwd: "xxxx",                         // Password for generating the key
    protocols: [socket.Protocol.TLSv12],    // Communication protocol
    useRemoteCipherPrefer: true,            // Whether to preferentially use the peer cipher suite
    signatureAlgorithms: "rsa_pss_rsae_sha256:ECDSA+SHA256",    // Signature algorithm
    cipherSuite: "AES256-SHA256",           // Cipher suite
  },
};

// Set up a connection.
tlsTwoWay.connect(options, (err, data) => {
  console.error(err);
  console.log(data);
});

// Enable the TCPSocket connection to be automatically closed after use. Then, disable listening for TCPSocket connection events.
tlsTwoWay.close((err) => {
  if (err) {
    console.log("close callback error = " + err);
  } else {
    console.log("close success");
  }
  tlsTwoWay.off('message');
  tlsTwoWay.off('connect');
  tlsTwoWay.off('close');
});

// Create a TLSSocket connection (for one-way authentication).
let tlsOneWay = socket.constructTLSSocketInstance(); // One way authentication

// Subscribe to TLSSocket connection events.
tlsTwoWay.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)
});
tlsTwoWay.on('connect', () => {
  console.log("on connect")
});
tlsTwoWay.on('close', () => {
  console.log("on close")
});

// Bind the local IP address and port number.
tlsOneWay.bind({address: '192.168.xxx.xxx', port: xxxx, family: 1}, err => {
  if (err) {
    console.log('bind fail');
    return;
  }
  console.log('bind success');
});

// Set the communication parameters.
let oneWayOptions = {
  address: {
    address: "192.168.xxx.xxx",
    port: xxxx,
    family: 1,
  },
  secureOptions: {
    ca: ["xxxx","xxxx"],            // CA certificate
    cipherSuite: "AES256-SHA256",   // Cipher suite
  },
};

// Set up a connection.
tlsOneWay.connect(oneWayOptions, (err, data) => {
  console.error(err);
  console.log(data);
});

// Enable the TCPSocket connection to be automatically closed after use. Then, disable listening for TCPSocket connection events.
tlsTwoWay.close((err) => {
  if (err) {
    console.log("close callback error = " + err);
  } else {
    console.log("close success");
  }
  tlsTwoWay.off('message');
  tlsTwoWay.off('connect');
  tlsTwoWay.off('close');
});