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+**/bin/
+**/obj/
+k8s/
+.git/
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+# Normalize line endings: store everything as LF in the repository.
+* text=auto eol=lf
+
+# Windows-only scripts keep CRLF on checkout
+*.ps1 text eol=crlf
+*.cmd text eol=crlf
+*.bat text eol=crlf
+
+# Binary files
+*.png binary
+*.jpg binary
+*.ico binary
+*.dll binary
+*.exe binary
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+bin/
+obj/
+*.user
+.vs/
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+FROM mcr.microsoft.com/dotnet/sdk:8.0-alpine AS build
+WORKDIR /src
+COPY src/TcpEcho/TcpEcho.csproj TcpEcho/
+RUN dotnet restore TcpEcho/TcpEcho.csproj
+COPY src/TcpEcho/ TcpEcho/
+RUN dotnet publish TcpEcho/TcpEcho.csproj -c Release -o /app --no-restore
+
+FROM mcr.microsoft.com/dotnet/runtime:8.0-alpine
+ARG VERSION=dev
+ARG REVISION=unknown
+ARG CREATED=""
+# OCI labels: Gitea's package registry displays these on the package page and, when
+# image.source matches a repository URL, links the package to that repository.
+LABEL org.opencontainers.image.title="tcp-echo-server" \
+      org.opencontainers.image.description="Minimal .NET 8 TCP echo server that prefixes every reply with its instance identifier. Deployed as two instances behind Traefik on ports 9098 and 9099." \
+      org.opencontainers.image.source="https://gitea.eitczech.com/public/tcp-echo-server" \
+      org.opencontainers.image.url="https://gitea.eitczech.com/public/tcp-echo-server" \
+      org.opencontainers.image.documentation="https://gitea.eitczech.com/public/tcp-echo-server/src/branch/main/README.md" \
+      org.opencontainers.image.vendor="eitczech" \
+      org.opencontainers.image.licenses="MIT" \
+      org.opencontainers.image.version="${VERSION}" \
+      org.opencontainers.image.revision="${REVISION}" \
+      org.opencontainers.image.created="${CREATED}"
+WORKDIR /app
+COPY --from=build /app .
+ENV PORT=9099
+EXPOSE 9099
+USER 1654
+ENTRYPOINT ["dotnet", "TcpEcho.dll"]
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+# tcp-echo
+
+Minimal .NET 8 TCP echo server. Every reply is prefixed with the instance identifier
+(`INSTANCE_ID` env var, falling back to the hostname), and a `[<id>] connected` line is sent on connect.
+
+Two instances are deployed behind Traefik:
+
+| Instance | INSTANCE_ID | External port |
+|----------|-------------|---------------|
+| a        | echo-a      | 9098          |
+| b        | echo-b      | 9099          |
+
+## Build and push
+
+Requires a prior `docker login gitea.eitczech.com`.
+
+```powershell
+./build-push.ps1 -Tag 1.0.0              # pushes gitea.eitczech.com/public/tcp-echo-server:1.0.0
+./build-push.ps1 -Tag 1.0.0 -AlsoLatest  # additionally pushes :latest
+```
+
+The manifests reference `gitea.eitczech.com/public/tcp-echo-server:latest`. To pin a specific tag either edit
+`k8s/instance-a.yaml` / `k8s/instance-b.yaml`, or after `kubectl apply -k` run:
+
+```sh
+kubectl -n tcp-echo set image deploy/tcp-echo-a deploy/tcp-echo-b tcp-echo=gitea.eitczech.com/public/tcp-echo-server:1.0.0
+```
+
+If the Gitea registry is private, create a pull secret in the namespace and reference it via `imagePullSecrets`.
+
+### Package description on Gitea
+
+The `Dockerfile` sets the standard OCI labels (`org.opencontainers.image.*`). Gitea reads them from the pushed
+image and shows them on the package page:
+
+| Label            | Shown as / effect                                                              |
+|------------------|--------------------------------------------------------------------------------|
+| `description`    | Package description text                                                       |
+| `source`         | Links the package to the repository with the same URL (repo must exist first)  |
+| `url`, `documentation`, `licenses`, `authors`, `vendor` | Metadata section on the package page   |
+| `version`, `revision`, `created` | Filled in by `build-push.ps1` from the tag, git commit and current time |
+
+To change the description, edit the `LABEL` in `Dockerfile` and rebuild. If the package was pushed before the
+repository existed, link it manually: package page -> **Settings** -> **Link to repository**.
+
+## Deploy
+
+```sh
+kubectl apply -k k8s/
+kubectl -n tcp-echo rollout status deploy/tcp-echo-a deploy/tcp-echo-b
+```
+
+`30-traefik-entrypoint.yaml` adds `tcpechoa` (9098) and `tcpechob` (9099) entrypoints to the k3s-managed
+Traefik (Traefik restarts once). For a Helm-managed Traefik, drop that file from `kustomization.yaml` and run:
+
+```sh
+helm upgrade traefik traefik/traefik -n kube-system --reuse-values -f k8s/traefik-values.yaml
+```
+
+If Traefik's Service is a LoadBalancer, make sure the cloud/VPS firewall allows TCP 9098 and 9099.
+
+## Test
+
+### Linux / macOS
+
+```sh
+$ nc <server-ip> 9098
+[echo-a] connected
+hello
+[echo-a] hello
+
+$ nc <server-ip> 9099
+[echo-b] connected
+hello
+[echo-b] hello
+```
+
+### Windows (PowerShell)
+
+Windows has no `nc`. Use the included script, which opens a TCP connection, prints the greeting,
+sends a message and prints the echoed reply:
+
+```powershell
+.	est-echo.ps1 -Server <server-ip> -Port 9098
+.	est-echo.ps1 -Server <server-ip> -Port 9099 -Message "ping"
+```
+
+Expected output:
+
+```
+Connecting to <server-ip>:9098 ...
+<- [echo-a] connected
+-> hello
+<- [echo-a] hello
+```
+
+Just to check the port is reachable (no echo):
+
+```powershell
+Test-NetConnection -ComputerName <server-ip> -Port 9098
+```
+
+For an interactive session, `telnet <server-ip> 9098` works if the Telnet Client feature is enabled
+(`Enable-WindowsOptionalFeature -Online -FeatureName TelnetClient`), or install `ncat` via `winget install Insecure.Nmap`.
+
+### Local test with Docker
+
+```powershell
+docker build -t tcp-echo:local .
+docker run --rm -d --name tcp-echo-test -e INSTANCE_ID=echo-local -p 9099:9099 tcp-echo:local
+.	est-echo.ps1 -Server localhost -Port 9099
+docker rm -f tcp-echo-test
+```
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+<#
+.SYNOPSIS
+    Builds the tcp-echo Docker image and pushes it to the Gitea registry.
+.EXAMPLE
+    .\build-push.ps1 -Tag 1.0.0
+    .\build-push.ps1 -Tag 1.0.0 -AlsoLatest
+#>
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory = $true, Position = 0)]
+    [ValidatePattern('^[A-Za-z0-9_][A-Za-z0-9_.-]{0,127}$')]
+    [string]$Tag,
+
+    # Also tag and push the image as :latest
+    [switch]$AlsoLatest
+)
+
+$ErrorActionPreference = 'Stop'
+$Registry = 'gitea.eitczech.com'
+$Repo     = "$Registry/public/tcp-echo-server"
+$Image    = "${Repo}:$Tag"
+$Root     = $PSScriptRoot
+
+function Invoke-Checked {
+    param([string[]]$Cmd)
+    Write-Host "> $($Cmd -join ' ')" -ForegroundColor Cyan
+    & $Cmd[0] $Cmd[1..($Cmd.Length - 1)]
+    if ($LASTEXITCODE -ne 0) { throw "Command failed with exit code ${LASTEXITCODE}: $($Cmd -join ' ')" }
+}
+
+# Metadata baked into OCI labels (shown on the Gitea package page)
+$Revision = 'unknown'
+if (Get-Command git -ErrorAction SilentlyContinue) {
+    $r = (& git -C $Root rev-parse --short HEAD 2>$null)
+    if ($LASTEXITCODE -eq 0 -and $r) { $Revision = $r.Trim() }
+}
+$Created = (Get-Date).ToUniversalTime().ToString('yyyy-MM-ddTHH:mm:ssZ')
+
+Write-Host "Building $Image (revision $Revision)" -ForegroundColor Green
+Invoke-Checked @('docker', 'build', '--pull',
+    '--build-arg', "VERSION=$Tag",
+    '--build-arg', "REVISION=$Revision",
+    '--build-arg', "CREATED=$Created",
+    '-t', $Image, $Root)
+
+if ($AlsoLatest) {
+    Invoke-Checked @('docker', 'tag', $Image, "${Repo}:latest")
+}
+
+Write-Host "Pushing $Image" -ForegroundColor Green
+Invoke-Checked @('docker', 'push', $Image)
+
+if ($AlsoLatest) {
+    Invoke-Checked @('docker', 'push', "${Repo}:latest")
+}
+
+Write-Host "Done: $Image" -ForegroundColor Green
+Write-Host "Deploy with:  kubectl -n tcp-echo set image deploy/tcp-echo-a deploy/tcp-echo-b tcp-echo=$Image"
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+apiVersion: v1
+kind: Namespace
+metadata:
+  name: tcp-echo
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+# Traefik must have static entrypoints on 9098/9099 before IngressRouteTCP can use them.
+# This is the k3s way (Traefik is installed via the bundled Helm chart). Traefik restarts once when applied.
+# If Traefik was installed with plain Helm instead, use k8s/traefik-values.yaml with `helm upgrade`.
+apiVersion: helm.cattle.io/v1
+kind: HelmChartConfig
+metadata:
+  name: traefik
+  namespace: kube-system
+spec:
+  valuesContent: |-
+    ports:
+      tcpechoa:
+        port: 9098
+        expose:
+          default: true
+        exposedPort: 9098
+        protocol: TCP
+      tcpechob:
+        port: 9099
+        expose:
+          default: true
+        exposedPort: 9099
+        protocol: TCP
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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: tcp-echo-a
+  namespace: tcp-echo
+  labels:
+    app: tcp-echo
+    instance: a
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: tcp-echo
+      instance: a
+  template:
+    metadata:
+      labels:
+        app: tcp-echo
+        instance: a
+    spec:
+      containers:
+        - name: tcp-echo
+          image: gitea.eitczech.com/public/tcp-echo-server:latest
+          imagePullPolicy: Always
+          env:
+            - name: PORT
+              value: "9098"
+            - name: INSTANCE_ID
+              value: "echo-a"
+          ports:
+            - name: tcp
+              containerPort: 9098
+              protocol: TCP
+          readinessProbe:
+            tcpSocket:
+              port: tcp
+            initialDelaySeconds: 2
+            periodSeconds: 5
+          livenessProbe:
+            tcpSocket:
+              port: tcp
+            initialDelaySeconds: 5
+            periodSeconds: 10
+          resources:
+            requests:
+              cpu: 20m
+              memory: 32Mi
+            limits:
+              cpu: 200m
+              memory: 128Mi
+          securityContext:
+            allowPrivilegeEscalation: false
+            runAsNonRoot: true
+            runAsUser: 1654
+            runAsGroup: 1654
+            capabilities:
+              drop: ["ALL"]
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: tcp-echo-a
+  namespace: tcp-echo
+spec:
+  type: ClusterIP
+  selector:
+    app: tcp-echo
+    instance: a
+  ports:
+    - name: tcp
+      port: 9098
+      targetPort: tcp
+      protocol: TCP
+---
+apiVersion: traefik.io/v1alpha1
+kind: IngressRouteTCP
+metadata:
+  name: tcp-echo-a
+  namespace: tcp-echo
+spec:
+  entryPoints:
+    - tcpechoa
+  routes:
+    - match: HostSNI(`*`)
+      services:
+        - name: tcp-echo-a
+          port: 9098
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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: tcp-echo-b
+  namespace: tcp-echo
+  labels:
+    app: tcp-echo
+    instance: b
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: tcp-echo
+      instance: b
+  template:
+    metadata:
+      labels:
+        app: tcp-echo
+        instance: b
+    spec:
+      containers:
+        - name: tcp-echo
+          image: gitea.eitczech.com/public/tcp-echo-server:latest
+          imagePullPolicy: Always
+          env:
+            - name: PORT
+              value: "9099"
+            - name: INSTANCE_ID
+              value: "echo-b"
+          ports:
+            - name: tcp
+              containerPort: 9099
+              protocol: TCP
+          readinessProbe:
+            tcpSocket:
+              port: tcp
+            initialDelaySeconds: 2
+            periodSeconds: 5
+          livenessProbe:
+            tcpSocket:
+              port: tcp
+            initialDelaySeconds: 5
+            periodSeconds: 10
+          resources:
+            requests:
+              cpu: 20m
+              memory: 32Mi
+            limits:
+              cpu: 200m
+              memory: 128Mi
+          securityContext:
+            allowPrivilegeEscalation: false
+            runAsNonRoot: true
+            runAsUser: 1654
+            runAsGroup: 1654
+            capabilities:
+              drop: ["ALL"]
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: tcp-echo-b
+  namespace: tcp-echo
+spec:
+  type: ClusterIP
+  selector:
+    app: tcp-echo
+    instance: b
+  ports:
+    - name: tcp
+      port: 9099
+      targetPort: tcp
+      protocol: TCP
+---
+apiVersion: traefik.io/v1alpha1
+kind: IngressRouteTCP
+metadata:
+  name: tcp-echo-b
+  namespace: tcp-echo
+spec:
+  entryPoints:
+    - tcpechob
+  routes:
+    - match: HostSNI(`*`)
+      services:
+        - name: tcp-echo-b
+          port: 9099
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+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+  - 00-namespace.yaml
+  - 30-traefik-entrypoint.yaml
+  - instance-a.yaml
+  - instance-b.yaml
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+# For non-k3s installs: helm upgrade traefik traefik/traefik -n <traefik-ns> --reuse-values -f k8s/traefik-values.yaml
+ports:
+  tcpechoa:
+    port: 9098
+    expose:
+      default: true
+    exposedPort: 9098
+    protocol: TCP
+  tcpechob:
+    port: 9099
+    expose:
+      default: true
+    exposedPort: 9099
+    protocol: TCP
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+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+
+var port = int.TryParse(Environment.GetEnvironmentVariable("PORT"), out var p) ? p : 9099;
+var instanceId = Environment.GetEnvironmentVariable("INSTANCE_ID") is { Length: > 0 } id
+    ? id
+    : Environment.MachineName;
+
+var listener = new TcpListener(IPAddress.Any, port);
+listener.Start();
+Console.WriteLine($"TCP echo server '{instanceId}' listening on 0.0.0.0:{port}");
+
+using var cts = new CancellationTokenSource();
+AppDomain.CurrentDomain.ProcessExit += (_, _) => cts.Cancel();
+Console.CancelKeyPress += (_, e) => { e.Cancel = true; cts.Cancel(); };
+
+try
+{
+    while (!cts.IsCancellationRequested)
+    {
+        var client = await listener.AcceptTcpClientAsync(cts.Token);
+        _ = HandleClientAsync(client, instanceId, cts.Token);
+    }
+}
+catch (OperationCanceledException) { }
+finally
+{
+    listener.Stop();
+    Console.WriteLine("Shutting down.");
+}
+
+static async Task HandleClientAsync(TcpClient client, string instanceId, CancellationToken ct)
+{
+    var remote = client.Client.RemoteEndPoint?.ToString() ?? "unknown";
+    Console.WriteLine($"Connected: {remote}");
+    try
+    {
+        using (client)
+        {
+            var stream = client.GetStream();
+
+            // Greeting so the caller knows which instance it reached even before sending anything.
+            await stream.WriteAsync(Encoding.UTF8.GetBytes($"[{instanceId}] connected\n"), ct);
+
+            var prefix = Encoding.UTF8.GetBytes($"[{instanceId}] ");
+            var buffer = new byte[4096];
+            var reply = new byte[prefix.Length + buffer.Length];
+            prefix.CopyTo(reply, 0);
+            int read;
+            while ((read = await stream.ReadAsync(buffer, ct)) > 0)
+            {
+                buffer.AsSpan(0, read).CopyTo(reply.AsSpan(prefix.Length));
+                await stream.WriteAsync(reply.AsMemory(0, prefix.Length + read), ct);
+            }
+        }
+    }
+    catch (Exception ex) when (ex is IOException or SocketException or OperationCanceledException)
+    {
+        // client went away or shutdown requested
+    }
+    Console.WriteLine($"Disconnected: {remote}");
+}
@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <InvariantGlobalization>true</InvariantGlobalization>
+  </PropertyGroup>
+</Project>
@@ -0,0 +1,54 @@
+<#
+.SYNOPSIS
+    Connects to a tcp-echo instance, prints the greeting, sends a message and prints the reply.
+.EXAMPLE
+    .\test-echo.ps1 -Server sparkyxf.cz -Port 9098
+    .\test-echo.ps1 -Server sparkyxf.cz -Port 9099 -Message "ping"
+#>
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory = $true, Position = 0)]
+    [string]$Server,
+
+    [Parameter(Mandatory = $true, Position = 1)]
+    [ValidateRange(1, 65535)]
+    [int]$Port,
+
+    [string]$Message = "hello",
+
+    [int]$TimeoutMs = 5000
+)
+
+$ErrorActionPreference = 'Stop'
+
+function Read-Line {
+    param([System.IO.StreamReader]$Reader)
+    $line = $Reader.ReadLine()
+    if ($null -eq $line) { throw "Connection closed by server." }
+    return $line
+}
+
+$client = New-Object System.Net.Sockets.TcpClient
+try {
+    $client.ReceiveTimeout = $TimeoutMs
+    $client.SendTimeout    = $TimeoutMs
+
+    Write-Host "Connecting to ${Server}:${Port} ..." -ForegroundColor Cyan
+    if (-not $client.ConnectAsync($Server, $Port).Wait($TimeoutMs)) {
+        throw "Connect to ${Server}:${Port} timed out after ${TimeoutMs} ms."
+    }
+
+    $stream = $client.GetStream()
+    $reader = New-Object System.IO.StreamReader($stream, [System.Text.Encoding]::UTF8)
+    $writer = New-Object System.IO.StreamWriter($stream, (New-Object System.Text.UTF8Encoding($false)))
+    $writer.NewLine   = "`n"
+    $writer.AutoFlush = $true
+
+    Write-Host "<- $(Read-Line $reader)" -ForegroundColor Green   # greeting: [instance] connected
+    Write-Host "-> $Message"
+    $writer.WriteLine($Message)
+    Write-Host "<- $(Read-Line $reader)" -ForegroundColor Green   # echo:     [instance] <message>
+}
+finally {
+    $client.Dispose()
+}