From 8b3deb21c179ec2c20ce3f9b64663c3cfa435f11 Mon Sep 17 00:00:00 2001
From: andig <andi@evcc.io>
Date: Mon, 3 Mar 2025 11:31:56 +0100
Subject: [PATCH] RCT: handle initial connection failing to read (#19362)

---
 go.mod                 | 2 +-
 go.sum                 | 4 ++--
 meter/rct.go           | 9 +++++++++
 meter/template_test.go | 1 +
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/go.mod b/go.mod
index 87772285d..c0061add5 100644
--- a/go.mod
+++ b/go.mod
@@ -222,4 +222,4 @@ replace github.com/grid-x/modbus => github.com/evcc-io/modbus v0.0.0-20241027151
 
 replace github.com/lorenzodonini/ocpp-go => github.com/evcc-io/ocpp-go v0.0.0-20241230132027-815870498cc3
 
-replace github.com/mlnoga/rct => github.com/andig/rct v0.1.2-0.20250302110530-e1b03e640f26
+replace github.com/mlnoga/rct => github.com/andig/rct v0.1.2-0.20250303102452-38b496bdd2c9
diff --git a/go.sum b/go.sum
index 3a48bba7c..f1ded472b 100644
--- a/go.sum
+++ b/go.sum
@@ -39,8 +39,8 @@ github.com/andig/gosunspec v0.0.0-20240918203654-860ce51d602b h1:81UMfM949I7StrR
 github.com/andig/gosunspec v0.0.0-20240918203654-860ce51d602b/go.mod h1:c6P6szcR+ROkqZruOR4f6qbDKFjZX6OitPpj+yJ/r8k=
 github.com/andig/mbserver v0.0.0-20230310211055-1d29cbb5820e h1:m/NTP3JWpR7M0ljLxiQU4fzR25jjhe1LDtxLMNcoNJQ=
 github.com/andig/mbserver v0.0.0-20230310211055-1d29cbb5820e/go.mod h1:4VtYzTm//oUipwvO3yh0g/udTE7pYJM+U/kyAuFDsgM=
-github.com/andig/rct v0.1.2-0.20250302110530-e1b03e640f26 h1:Kqq17bxhK6TsBs54gf2Bk4pghBAAeJw1WN/RU0pgV1M=
-github.com/andig/rct v0.1.2-0.20250302110530-e1b03e640f26/go.mod h1:KRjBDV8kuvGd2kJfN8/F0kjH8JjkFVpBpn7MhW+ACL8=
+github.com/andig/rct v0.1.2-0.20250303102452-38b496bdd2c9 h1:hHUPfKTJlyHX0i5iZy7UNtIYoNDtcPH/Q1bbOe2OZ+g=
+github.com/andig/rct v0.1.2-0.20250303102452-38b496bdd2c9/go.mod h1:KRjBDV8kuvGd2kJfN8/F0kjH8JjkFVpBpn7MhW+ACL8=
 github.com/andig/yaml v0.0.0-20240531135838-1ff5761ab467 h1:JqIoHxsQSV39xaemvVRu3HOkSf5AbhQ1YEENJa2cL3Q=
 github.com/andig/yaml v0.0.0-20240531135838-1ff5761ab467/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 github.com/andybalholm/cascadia v1.3.3 h1:AG2YHrzJIm4BZ19iwJ/DAua6Btl3IwJX+VI4kktS1LM=
diff --git a/meter/rct.go b/meter/rct.go
index 1ba17a762..bd2b577f0 100644
--- a/meter/rct.go
+++ b/meter/rct.go
@@ -6,7 +6,9 @@ import (
 	"errors"
 	"fmt"
 	"math"
+	"math/rand/v2"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/evcc-io/evcc/api"
@@ -20,6 +22,8 @@ type RCT struct {
 	usage string          // grid, pv, battery
 }
 
+var rctMu sync.Mutex
+
 func init() {
 	registry.AddCtx("rct", NewRCTFromConfig)
 }
@@ -52,6 +56,11 @@ func NewRCTFromConfig(ctx context.Context, other map[string]interface{}) (api.Me
 func NewRCT(ctx context.Context, uri, usage string, minSoc, maxSoc int, cache time.Duration, capacity func() float64) (api.Meter, error) {
 	log := util.NewLogger("rct")
 
+	// prevent concurrent connections
+	rctMu.Lock()
+	time.Sleep(time.Duration(rand.Uint64N(uint64(time.Second))))
+	rctMu.Unlock()
+
 	conn, err := rct.NewConnection(ctx, uri, rct.WithErrorCallback(func(err error) {
 		if err != nil {
 			log.ERROR.Println(err)
diff --git a/meter/template_test.go b/meter/template_test.go
index 0cdae033f..619db2f5e 100644
--- a/meter/template_test.go
+++ b/meter/template_test.go
@@ -23,6 +23,7 @@ var acceptable = []string{
 	"connect: connection refused",
 	"connect: network is unreachable",
 	"i/o timeout",
+	"timeout",                      // RCT
 	"'sma': missing uri or serial", // SMA
 	"[1ESY1161052714 1ESY1161229249 1EMH0008842285 1ESY1161978584 1EMH0004864048 1ESY1161979033 7ELS8135823805]", // Discovergy
 	"can only have either uri or device",                                   // modbus