tcp-netx

Synchronous and Asynchronous access to TCP servers using basic TCP sockets or HTTP from Node.js.

Chris Munt [email protected]
21 May 2024, MGateway Ltd http://www.mgateway.com

• Verified to work with Node.js v4 to v22.
• Release Notes can be found at the end of this document.

Contents

• Acknowledgements
• Prerequisites
• Installing tcp-netx
• Connecting to the server
• Reading and Writing
• HTTP requests
• Troubleshooting
• Using Node.js/V8 worker threads
• License

Acknowledgements

Special thanks to the Ripple Foundation https://www.ripple.foundation/ for support and funding the initial phase of this project.

Prerequisites

tcp-netx is a Node.js addon written in C++. It is distributed as C++ source code and the NPM installation procedure will expect a C++ compiler to be present on the target system.

Linux systems can use the freely available GNU C++ compiler (g++) which can be installed as follows.

Ubuntu:

   apt-get install g++

Red Hat and CentOS:

   yum install gcc-c++

Apple OS X can use the freely available Xcode development environment.

There are two options for Windows, both of which are free:

• Microsoft Visual Studio Community: https://www.visualstudio.com/vs/community/
• MinGW: http://www.mingw.org/

If the Windows machine is not set up for systems development, building native Addon modules for this platform from C++ source can be quite arduous. There is some helpful advice available at:

• Compiling native Addon modules for Windows

Alternatively there are built Windows x64 binaries available from:

• https://github.com/chrisemunt/tcp-netx/blob/master/bin/winx64

Installing tcp-netx

Assuming that Node.js is already installed and a C++ compiler is available to the installation process:

   npm install tcp-netx

This command will create the tcp-netx addon (tcp-netx.node).

Connecting to the server

Most tcp-netx methods are capable of operating either synchronously or asynchronously. For an operation to complete asynchronously, simply supply a suitable callback as the last argument in the call.

The first step is to add tcp-netx to your Node.js script

   var tcp = require('tcp-netx');

Create a Server Object

The second step is to create a Server Object. This method does not actually create a connection; it simply registers the server host name and the TCP port on which it is listening.

   var db = new tcp.server(<server name>, <port>);

For example, create a server connection object for a local web server listening on the well known port for HTTP (80).

   var db = new tcp.server("localhost", 80);

Return the version of tcp-netx

   var result = db.version();

Example:

   console.log("\nTCP-NETX Version: " + db.version());

Modify the default timeout for tcp-netx methods

The default timeout applied to all tcp-netx methods is 10 seconds. The timeout() method can be used to modify this value.

   var timeout = db.timeout([modified timeout]);

Timeouts for tcp-netx methods are specified in seconds.

Example 1 (returning the existing timeout value):

   var timeout = db.timeout();

Example 2 (resetting the default timeout to 30 seconds):

   var timeout = db.timeout(30);

Several methods allow for the timeout to be modified on a per-operation basis.

Connect to the Server

Having created a Server Object, a connection can be made.

Optionally, the connect() method may be supplied with an object to specify a timeout for the connect operation (in seconds).

Synchronous:

   var result = db.connect([{timeout: <timeout>}]);

Asynchronous:

   db.connect([{timeout: <timeout>}, ]callback(<error>, <result>));
  

Result Object:

   {
      ok: <ok flag>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }
 

If the operation is successful, the ok flag will be set to true. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

Example 1 (connect to the server using the default timeout):

   var result = db.connect();

Example 2 (connect to the server with a timeout of 60 seconds):

   var result = db.connect({timeout: 60});

Disconnect from the Server

Synchronous:

   var result = db.disconnect();

Asynchronous:

   db.disconnect(callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }
 

If the operation is successful, the ok flag will be set to true. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

Reading and Writing

Write to the Server

The default character encoding for the write() method is UTF8. To write binary data to the server use the writebinary() method instead.

The request object sent to the server must contain the data field.

Synchronous:

   var result = db.write({data: <data>});

Asynchronous:

   db.write({data: <data>}, callback(<error>, <result>));
  

Result Object:

   {
      ok: <ok flag>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }
 

If the operation is successful, the ok flag will be set to true. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

Example: Send "PING" to the server

   var result = db.write({data: "PING"});

   

Read from the Server

The default character encoding for the read() method is UTF8. To read binary data from the server use the readbinary() method instead.

Optionally, the read() method may be supplied with an object to specify the length of the data to be read and a timeout may also be specified (in seconds).

Synchronous:

   var result = db.read([{[timeout: <timeout>] [, length: <length>]}]);

Asynchronous:

   db.read([{[timeout: <timeout>] [, length: <length>]}], callback(<error>, <result>));
   

Result Object:

   {
      ok: <ok flag>,
      data: <data>,
      eof: <eof>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }
 

If the operation is successful, the ok flag will be set to true and the response data will be returned. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

If the eof flag is set then it must be assumed that the server closed the connection - either as a result of an error condition or timeout.

If no length is specified, the method will return as much data as is currently available. Otherwise the method will block until it has received the requested amount of data from the server.

Example: Read 4 Bytes from the server with a timeout of 30 seconds

   var result = db.read({length: 4, timeout: 30});

HTTP requests

Sending an HTTP Request to a Web Server

The request object sent to the web server must, at the very least, contain the HTTP request headers in the headers field. Optionally, the request may include a payload in the content field and a timeout may also be specified (in seconds).

Synchronous:

   var result = db.http({headers: <headers> [, content: <content>] [, timeout: <timeout>]});

Asynchronous:

   db.http({headers: <headers> [, content: <content>]  [, timeout: <timeout>]}, callback(<error>, <result>));
   

Result Object:

   {
      ok: <ok flag>,
      headers: <headers>,
      keepalive: <keepalive flag>
      [, content: <content>]
      [, eof: <eof>]
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }
 

If the operation is successful, the ok flag will be set to true and the response headers and any content (i.e. payload) will be returned. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

If the eof flag is set then it must be assumed that the server closed the connection - either as a result of an error condition or timeout.

If the HTTP keepalive flag is set then it is possible to send a further HTTP request without reconnecting to the web server.

Example: Request /index.html from the web server

   var result = db.http({headers: "GET /index.html HTTP/1.1\r\nHost: localhost:80\r\nConnection: close\r\n\r\n"});

Using Node.js/V8 worker threads

tcp-netx functionality can now be used with Node.js/V8 worker threads. This enhancement is available with Node.js v12 (and later).

The following scheme illustrates how tcp-netx should be used in threaded Node.js applications.

   const { Worker, isMainThread, parentPort, threadId } = require('worker_threads');

   if (isMainThread) {
      // start the threads
      const worker1 = new Worker(__filename);
      const worker2 = new Worker(__filename);

      // process messages received from threads
      worker1.on('message', (message) => {
         console.log(message);
      });
      worker2.on('message', (message) => {
         console.log(message);
      });
   } else {
      var tcp = require('tcp-netx');
      var db = new tcp.server(<server>, <port>);
      var result = db.connect();

      // do some work

      var result = db.disconnect();
      // tell the parent that we're done
      parentPort.postMessage("threadId=" + threadId + " Done");
   }

Troubleshooting

tcp-netx contains a function call trace and logging facility to help with troubleshooting problems in operation.

To write a running commentary of progress to the console window:

   var result = db.settrace(1);

To write a running commentary of progress to a file:

   var result = db.settrace("/tmp/tcp-netx.log");

To disable the trace facility:

   var result = db.settrace(0);

License

Copyright (c) 2016-2024 MGateway Ltd, Surrey UK.
All rights reserved.

http://www.mgateway.com
Email: [email protected]

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Release Notes

v1.0.7 (2 December 2016)

• Initial Release

v1.1.8 (19 July 2019)

• Support for Node.js v8, v10 and v12.
• Support for sending and receiving binary data: readbinary() and writebinary() methods.

v1.1.9 (12 September 2019)

• Internal changes to replace V8/Node.js API functionality that was deprecated in Node.js v12.

v1.1.10 (8 November 2019)

• Correct a fault in the processing of HTTP POST requests in the db.http() method.

v1.2.11 (6 May 2020)

• Verify that tcp-netx will build and work with Node.js v14.x.x.
• Introduce support for Node.js/V8 worker threads (for Node.js v12.x.x. and later).
  • See the section on 'Using Node.js/V8 worker threads'.
• Correct a fault in the processing of error conditions (e.g. 'server not available' etc..).
• Suppress a number of benign 'cast-function-type' compiler warnings when building on the Raspberry Pi.

v1.2.12 (28 April 2021)

• Verify that tcp-netx will build and work with Node.js v16.x.x.
• A number of faults related to the use of tcp-netx functionality in Node.js/v8 worker threads have been corrected. In particular, it was noticed that callback functions were not being fired correctly for some asynchronous invocations of tcp-netx methods.

v1.2.12a (25 April 2022)

• Verify that tcp-netx will build and work with Node.js v18.x.x.

v1.3.13 (14 December 2022)

• Correct a fault in the processing of timeouts specified in the read() and http() methods.
• Allow a timeout to be specified for the connect() method.
• Introduce a timeout() method to allow the default timeout applied to all tcp-netx methods to be changed. The initial default timeout for all methods is set to 10 seconds.

v1.3.13a (3 May 2023)

• Verify that tcp-netx will build and work with Node.js v20.x.x.

v1.3.13b (22 June 2023)

• Documentation update.

v1.4.14 (18 July 2023)

• Introduce support for Alpine Linux.

v1.4.14a (21 May 2024)

• Verify that tcp-netx will build and work with Node.js v22.x.x.