Building a JSON-RPC Server in Go and a PHP Client with Common Pitfalls

JSON-RPC is a stateless, lightweight remote procedure call protocol that uses JSON for data exchange. Go provides both rpc and jsonrpc packages, the latter enabling cross‑platform communication. This article demonstrates how to quickly build a JSON‑RPC server in Go and a client in PHP, and records common pitfalls encountered.

1. Implementing the jsonrpc_server in Go

2.1 Import packages

import (
    "net/rpc"
    "net"
    "log"
    "net/rpc/jsonrpc"
    "fmt"
)

2.2 Define RPC methods

type Edwin int

func (this *Edwin) Add(args map[string]float64, res *float64) error {
    *res = args["num1"] + args["num2"]
    return nil
}

func (this *Edwin) Multi(args map[string]interface{}, res *float64) error {
    *res = args["num1"].(float64) * args["num2"].(float64)
    return nil
}

2.3 Register handler and start listening

rpc.Register(new(Edwin))
l, err := net.Listen("tcp", ":11223")
if err != nil {
    log.Fatalln("listen error:", err)
}
for {
    conn, err := l.Accept()
    if err != nil {
        log.Fatalln("accept failed:", err)
    }
    fmt.Println("jsonrpc server  start listen on 11223...")
    go func(conn net.Conn) {
        fmt.Println("a new connection is coming...")
        jsonrpc.ServeConn(conn)
    }(conn)
}

3. Implementing the jsonrpc_client in PHP

class JsonRpc {
    private $conn;
    function __construct($host, $port) {
        $this->conn = fsockopen($host, $port, $errno, $errStr, 2);
    }
    public function call($method, $params) {
        $err = fwrite($this->conn, json_encode([
            'method' => $method,
            'params' => array($params),
            'id' => 1,
        ]));
        if (empty($err)) {
            return false;
        }
        stream_set_timeout($this->conn, 0, 300);
        $line = fgets($this->conn);
        if ($line === false) {
            return NULL;
        }
        fclose($this->conn);
        return json_decode($line, true);
    }
}
$client = new JsonRPC("127.0.0.1", 11223);
$client2 = new JsonRPC("127.0.0.1", 11223);
$ret = $client->Call("Edwin2.Multi", array("num1"=>14, "num2"=>20));
$ret2 = $client2->Call("Edwin2.Add", array("num1"=>14, "num2"=>20));
var_export($ret);
var_export($ret2);

4. Verification and common issues

Running the Go server prints listening messages, and the PHP client returns results such as array('id'=>1,'result'=>280,'error'=>NULL). A common pitfall is passing 'params' => $params directly; Go's jsonrpc implementation expects params to be an array, otherwise unmarshalling fails with “json: cannot unmarshal object into Go value of type [1]interface {}”. This reveals that Go's jsonrpc does not fully follow the JSON‑RPC specification.

5. Internal processing flow

(Diagram omitted in text.)