Network Communications

Packaged apps can act as a network client for TCP and UDP connections. This doc shows you how to use TCP and UDP to send and receive data over the network. For more information, see the Sockets API.

API Samples: Want to play with the code? Check out the telnet and udp samples.

Manifest requirements

For packaged apps that use TCP or UDP, add the "socket" permission to the manifest and specify the IP end point permission rules. For example:

"permissions": [
    {"socket": [
      "rule1",
      "rule2",
      ...
    ]}
  ]

The syntax of socket permission rules follows these patterns:

<socket-permission-rule>
     := <op> | <op> ':' <host> | <op> ':' ':' <port> |
        <op> ':' <host> ':' <port>
 <op> := 'tcp-connect' | 'tcp-listen' | 'udp-bind' | 'udp-send-to'
 <host> := '*' | '*.' <anychar except '/' and '*'>+
 <port> := '*' | <port number between 1 and 65535>)

Examples of socket permission rules:

• "tcp-connect:*:23" – connecting on port 23 of any hosts
• "tcp-connect:www.example.com:23" – connecting port 23 of www.example.com
• "tcp-connect" – connecting any ports of any hosts
• "udp-send-to::99" – sending UDP packet to port 99 of any hosts
• "udp-bind::8899" – binding local port 8899 to receive UDP package
• "tcp-listen::8080" – TCP listening on local port 8080

Using TCP

Packaged apps can make connections to any service that supports TCP.

Connecting to a socket

Here's a sample showing how to connect ($ref:socket.connect) to a socket:

chrome.socket.create('tcp', {}, function(createInfo) {
  chrome.socket.connect(createInfo.socketId, IP, PORT, onConnectedCallback);
});

Keep a handle to the socketId so that you can later read and write ($ref:socket.write) to this socket.

chrome.socket.write(socketId, arrayBuffer, onWriteCompleteCallback);

Reading to & writing from a socket

Reading ($ref:socket.read) and writing from a socket uses ArrayBuffer objects. To learn about ArrayBuffers, check out the overview, JavaScript typed arrays, and the tutorial, How to convert ArrayBuffer to and from String.

chrome.socket.read(socketId, null, function(readInfo) {
  if (readInfo.resultCode > 0) {
    // readInfo.data is an arrayBuffer.
  }
});

Disconnecting from a socket

Here's how to disconnect ($ref:socket.disconnect):

chrome.socket.disconnect(socketId);

Using UDP

Packaged apps can make connections to any service that supports UDP.

Sending data

Here's a sample showing how to send data over the network using UDP:

// Create the Socket
chrome.socket.create('udp', '127.0.0.1', 1337, {},
 function(socketInfo) {
   // The socket is created, now we want to connect to the service
   var socketId = socketInfo.socketId;
   chrome.socket.connect(socketId, function(result) {
     // We are now connected to the socket so send it some data
     chrome.socket.write(socketId, arrayBuffer,
       function(sendInfo) {
         console.log("wrote " + sendInfo.bytesWritten);
       }
     );
   });
 }
);

Receiving data

This example is very similar to the 'Sending data' example with the addition of a special handler in the 'create' method. The parameter is an object with one value 'onEvent' that is a function reference to the method that will be called when data is available on the port.

// Handle the data response
var handleDataEvent = function(d) {
  var data = chrome.socket.read(d.socketId);
  console.log(data);
};

// Create the Socket
chrome.socket.create('udp', '127.0.0.1', 1337, { onEvent: handleDataEvent },
 function(socketInfo) {
   // The socket is created, now we want to connect to the service
   var socketId = socketInfo.socketId;
   chrome.socket.connect(socketId, function(result) {
     // We are now connected to the socket so send it some data
     chrome.socket.write(socketId, arrayBuffer,
       function(sendInfo) {
         console.log("wrote " + sendInfo.bytesWritten);
       }
     );
   });
 }
);

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