What it is
POCO (Portable Components) is a set of modern C++ libraries that provide building blocks for network-centric, portable applications. It includes modules for networking, HTTP, XML, JSON, threading, file system access, and more.
POCO offers modules such as Foundation (core utilities), Net (networking), NetSSL (SSL/TLS), Util (configuration and logging), JSON, and XML. It supports asynchronous programming, HTTP clients/servers, file system utilities, and more.
Installation
sudo apt install libpoco-devGetting started
The smallest useful thing you can do with it, and what each part means.
#include <Poco/Net/HTTPClientSession.h>
#include <Poco/Net/HTTPRequest.h>
#include <Poco/Net/HTTPResponse.h>
#include <Poco/StreamCopier.h>
#include <iostream>
#include <sstream>
int main() {
Poco::Net::HTTPClientSession session("www.example.com");
Poco::Net::HTTPRequest req(Poco::Net::HTTPRequest::HTTP_GET, "/");
session.sendRequest(req);
Poco::Net::HTTPResponse res;
std::istream &is = session.receiveResponse(res);
std::stringstream ss;
Poco::StreamCopier::copyStream(is, ss);
std::cout << ss.str() << std::endl;
return 0;
}#include <Poco/File.h>
#include <iostream>
int main() {
Poco::File file("test.txt");
if (!file.exists()) {
file.createFile();
std::cout << "File created." << std::endl;
}
return 0;
}Advanced usage
Where the library earns its place over a simpler alternative.
// Use Poco::Thread and Poco::Runnable to implement threaded tasks.// Use Poco::JSON::Parser and Poco::JSON::Object to read/write JSON data.// Use Poco::Net::HTTPServer, HTTPRequestHandler, and HTTPRequestHandlerFactory to create a server.Errors and fixes
The failures you are most likely to hit, and what actually resolves them.
- Poco::IOException
- Occurs during file or network I/O. Check paths, network availability, and permissions.
- Poco::Net::HTTPException
- Thrown for HTTP request/response issues. Verify URLs, request formatting, and server availability.
Best practices
- Use Foundation module for core utilities like threading, timers, and file system operations.
- Leverage Net and NetSSL for network programming and secure connections.
- Use JSON and XML modules for structured data handling.
- Separate logic into reusable components for maintainability.
- Properly handle exceptions from POCO modules to avoid runtime crashes.
Background
Why it exists, and what it was reacting to.
POCO was created by Günter Obiltschnig in 2005 to simplify C++ development for networked and portable applications. It focuses on providing robust, reusable, and modern C++ components while remaining lightweight and easy to integrate.