diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..3932bb4
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,74 @@
+name: CI
+
+on: push
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version-file: "go.mod"
+          cache: false # golangci-lint-action does caching
+
+      - name: Lint
+        uses: golangci/golangci-lint-action@v3
+
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version-file: "go.mod"
+
+      - name: Test
+        run: go test -race -v ./...
+
+  build:
+    name: Build
+    needs: [lint, test]
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    strategy:
+      matrix:
+        os: ["linux", "darwin"]
+        arch: ["amd64", "arm64"]
+    env:
+      app: transmission-gluetun-port.${{ matrix.os }}-${{ matrix.arch }}
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version-file: "go.mod"
+
+      - name: Build
+        run: go build -o ${{ env.app }} -v ./...
+        env:
+          GOOS: ${{ matrix.os }}
+          GOARCH: ${{ matrix.arch }}
+
+      - name: Upload
+        uses: actions/upload-artifact@v3
+        with:
+          name: ${{ env.app }}
+          path: ${{ env.app }}
+          if-no-files-found: error
diff --git a/.rtx.toml b/.rtx.toml
new file mode 100644
index 0000000..fabed83
--- /dev/null
+++ b/.rtx.toml
@@ -0,0 +1,2 @@
+[tools]
+go = "1.21"
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..321ed72
--- /dev/null
+++ b/README.md
@@ -0,0 +1,22 @@
+# transmission-gluetun-port update
+
+Small go binary to periodically update the port of transmission based on gluten port forwarding status.
+
+Based on [transmission-nat-pmp](https://github.com/jordanpotter/transmission-nat-pmp).
+
+## Usage
+
+```bash
+transmission-gluetun-port -h
+```
+
+## Available environment variables
+
+| Name | Description | Default |
+|------|-------------|---------|
+| `TRANSMISSION_USER` | Transmission user | - |
+| `TRANSMISSION_PASSWORD` | Transmission password | - |
+| `GLUETUN_HOST` | Gluetun api host | `127.0.0.1` |
+| `GLUETUN_PORT` | Gluetun api port | `8000` |
+| `CHECK_INTERVAL` | Update interval ([format](https://pkg.go.dev/time#ParseDuration)) | `1m` |
+| `ERROR_INTERVAL` | Update interval in case of error ([format](https://pkg.go.dev/time#ParseDuration)) | `5s` |
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..092e888
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,14 @@
+module github.com/Michsior14/transmission-gluetun-port-update
+
+go 1.20
+
+require (
+	github.com/go-resty/resty/v2 v2.10.0
+	github.com/hekmon/transmissionrpc/v2 v2.0.1
+)
+
+require (
+	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect
+	github.com/hekmon/cunits/v2 v2.1.0 // indirect
+	golang.org/x/net v0.18.0 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..a761360
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,51 @@
+github.com/go-resty/resty/v2 v2.10.0 h1:Qla4W/+TMmv0fOeeRqzEpXPLfTUnR5HZ1+lGs+CkiCo=
+github.com/go-resty/resty/v2 v2.10.0/go.mod h1:iiP/OpA0CkcL3IGt1O0+/SIItFUbkkyw5BGXiVdTu+A=
+github.com/hashicorp/go-cleanhttp v0.5.2 h1:035FKYIWjmULyFRBKPs8TBQoi0x6d9G4xc9neXJWAZQ=
+github.com/hashicorp/go-cleanhttp v0.5.2/go.mod h1:kO/YDlP8L1346E6Sodw+PrpBSV4/SoxCXGY6BqNFT48=
+github.com/hekmon/cunits/v2 v2.1.0 h1:k6wIjc4PlacNOHwKEMBgWV2/c8jyD4eRMs5mR1BBhI0=
+github.com/hekmon/cunits/v2 v2.1.0/go.mod h1:9r1TycXYXaTmEWlAIfFV8JT+Xo59U96yUJAYHxzii2M=
+github.com/hekmon/transmissionrpc/v2 v2.0.1 h1:WkILCEdbNy3n/N/w7mi449waMPdH2AA1THyw7TfnN/w=
+github.com/hekmon/transmissionrpc/v2 v2.0.1/go.mod h1:+s96Pkg7dIP3h2PT3fzhXPvNb3OdLryh5J8PIvQg3aA=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/crypto v0.14.0/go.mod h1:MVFd36DqK4CsrnJYDkBA3VC4m2GkXAM0PvzMCn4JQf4=
+golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
+golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
+golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
+golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
+golang.org/x/net v0.17.0/go.mod h1:NxSsAGuq816PNPmqtQdLE42eU2Fs7NoRIZrHJAlaCOE=
+golang.org/x/net v0.18.0 h1:mIYleuAkSbHh0tCv7RvjL3F6ZVbLjq4+R7zbOn3Kokg=
+golang.org/x/net v0.18.0/go.mod h1:/czyP5RqHAH4odGYxBJ1qz0+CE5WZ+2j1YgoEo8F2jQ=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
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diff --git a/main.go b/main.go
new file mode 100644
index 0000000..528d079
--- /dev/null
+++ b/main.go
@@ -0,0 +1,100 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"github.com/go-resty/resty/v2"
+	"github.com/hekmon/transmissionrpc/v2"
+)
+
+type GluetunResponse struct {
+	Port uint16
+}
+
+var (
+	transmissionHostname = flag.String("transmission-hostname", "127.0.0.1", "transmission hostname")
+	transmissionPort     = flag.Int("transmission-port", 9091, "transmission port")
+	transmissionUsername = os.Getenv("TRANSMISSION_USERNAME")
+	transmissionPassword = os.Getenv("TRANSMISSION_PASSWORD")
+
+	gluetunHostname = getEnv("GLUETUN_HOSTNAME", "127.0.0.1")
+	gluetunPort     = getEnv("GLUETUN_PORT", "8000")
+
+	checkIntervalStr = getEnv("CHECK_INTERVAL", "1m")
+	errorIntervalStr = getEnv("ERROR_INTERVAL", "5s")
+)
+
+func init() {
+	flag.Parse()
+}
+
+func main() {
+	checkInterval, _ := time.ParseDuration(checkIntervalStr)
+	errorInterval, _ := time.ParseDuration(errorIntervalStr)
+	previousExternalPort := uint16(0)
+	gluetunPortApi := fmt.Sprintf("http://%s:%s/v1/openvpn/portforwarded", gluetunHostname, gluetunPort)
+	errorCount := 0
+	maxErrorCount := 5
+
+	httpClient := resty.New()
+
+	transmissionClient, err := transmissionrpc.New(*transmissionHostname, transmissionUsername, transmissionPassword, &transmissionrpc.AdvancedConfig{
+		Port: uint16(*transmissionPort),
+	})
+	if err != nil {
+		log.Fatalf("failed to create transmission client: %v", err)
+	}
+
+	for {
+		portMapping := &GluetunResponse{}
+		resp, err := httpClient.R().
+			SetResult(portMapping).
+			ForceContentType("application/json").
+			Get(gluetunPortApi)
+
+		if err != nil || resp.IsError() {
+			log.Fatalf("failed to fetch port mapping from gluetun: %v, %d", err, resp.StatusCode())
+		}
+
+		if portMapping.Port == 0 {
+			err = errors.New("empty port")
+			log.Printf("new port is not yet assigned, %v", err)
+		} else if portMapping.Port == previousExternalPort {
+			log.Printf("external port is unchanged: %d", portMapping.Port)
+		} else {
+			log.Printf("external port changed to: %d", portMapping.Port)
+
+			transmissionPeerPort := int64(portMapping.Port)
+			err = transmissionClient.SessionArgumentsSet(context.Background(), transmissionrpc.SessionArguments{
+				PeerPort: &transmissionPeerPort,
+			})
+			if err != nil {
+				log.Fatalf("failed to set transmission peer port: %v", err)
+			}
+			previousExternalPort = portMapping.Port
+			log.Printf("updated transmission peer port to: %d", transmissionPeerPort)
+		}
+
+		if err != nil && errorCount < maxErrorCount {
+			time.Sleep(errorInterval)
+			errorCount++
+		} else {
+			time.Sleep(checkInterval)
+			errorCount = 0
+		}
+	}
+}
+
+func getEnv(key, fallback string) string {
+	value := os.Getenv(key)
+	if len(value) == 0 {
+		return fallback
+	}
+	return value
+}