PathParams - capturing <tt>:name</tt> path segments

Layer: L7 Application · Build flags: none (core features only)

What this example teaches

A route path can contain :name segments that capture the matching part of the request path; you read the captured value back with http_get_param(). Literal segments must match exactly, and a route may capture up to MAX_PATH_PARAMS (default 4) segments.

Declaring and reading params. Put :id (etc.) in the path; in the handler, http_get_param(req, "id") returns the captured value:

// route: /users/:id
const char *id = http_get_param(req, "id");
// route: /users/:id/posts/:slug  -> two captures
const char *slug = http_get_param(req, "slug");

Registration order matters. Routes are matched in the order they are registered, so register the more specific route first - here /users/:id/posts/:slug before /users/:id, otherwise the latter would also match the former's paths:

server.on("/users/:id/posts/:slug", HttpMethod::HTTP_GET, handle_user_post); // more specific first
server.on("/users/:id", HttpMethod::HTTP_GET, handle_user);

For pattern matching beyond simple segments (numeric-only, file extensions), see RegexRoutes.

Build and run

pio ci --board=esp32dev --project-option="framework=arduino" \
  --lib="." examples/L7-Application/PathParams/PathParams.ino

curl http://<ip>/users/42
curl http://<ip>/users/42/posts/hello-world

Annotated source

The complete sketch (PathParams.ino), reproduced verbatim with added explanatory comments:

// Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
#include "protocore.h"
#include "network_drivers/physical/physical.h"
 
static const char *SSID = "YOUR_SSID";
static const char *PASSWORD = "YOUR_PASSWORD";
 
PC server;
 
// GET /users/:id  - one captured segment.
void handle_user(uint8_t slot_id, HttpReq *req)
{
    const char *id = http_get_param(req, "id"); // nullptr if absent
    char body[96];
    snprintf(body, sizeof(body), "{\"user_id\":\"%s\"}", id ? id : "?");
    server.send(slot_id, 200, "application/json", body);
}
 
// GET /users/:id/posts/:slug  - two captured segments.
void handle_user_post(uint8_t slot_id, HttpReq *req)
{
    const char *id = http_get_param(req, "id");
    const char *slug = http_get_param(req, "slug");
    char body[160];
    snprintf(body, sizeof(body), "{\"user_id\":\"%s\",\"slug\":\"%s\"}", id ? id : "?", slug ? slug : "?");
    server.send(slot_id, 200, "application/json", body);
}
 
void setup()
{
    Serial.begin(115200);
 
    init_wifi_physical(SSID, PASSWORD);
    Serial.print("Connecting to WiFi");
    while (!wifi_ready())
    {
        delay(250);
        Serial.print('.');
    }
    uint32_t ip = pc_net_egress_ip(); // library egress IP (network byte order), no Arduino WiFi
    Serial.printf("IP: %u.%u.%u.%u\n", (unsigned)(ip & 0xFF), (unsigned)((ip >> 8) & 0xFF),
                  (unsigned)((ip >> 16) & 0xFF), (unsigned)((ip >> 24) & 0xFF));
 
 
    // Register the more specific route first; routes match in registration order.
    server.on("/users/:id/posts/:slug", HttpMethod::HTTP_GET, handle_user_post);
    server.on("/users/:id", HttpMethod::HTTP_GET, handle_user);
 
    int32_t result = server.begin(80);
    if (result < 0)
    {
        Serial.printf("begin() failed (error %d)\n", result);
        return;
    }
    Serial.println("Server started on port 80");
}
 
void loop()
{
    server.handle();
}