diff --git a/docs/advanced.rst b/docs/advanced.rst
index 681204f..992e035 100644
--- a/docs/advanced.rst
+++ b/docs/advanced.rst
@@ -73,6 +73,8 @@ Available environment variables
 | GOKAPI_MAX_MEMORY_UPLOAD | Sets the amount of RAM in MB that can be allocated for an upload.            | Yes         | 20                          |
 |                          | Any upload with a size greater than that will be written to a temporary file |             |                             |
 +--------------------------+------------------------------------------------------------------------------+-------------+-----------------------------+
+| GOKAPI_PORT              | Sets the webserver port                                                      | Yes         | 53842                       |
++--------------------------+------------------------------------------------------------------------------+-------------+-----------------------------+
 | TMPDIR                   | Sets the path which contains temporary files                                 | No          | Non-Docker: Default OS path |
 |                          |                                                                              |             | Docker:     [DATA_DIR]      |
 +--------------------------+------------------------------------------------------------------------------+-------------+-----------------------------+
diff --git a/internal/configuration/setup/Setup.go b/internal/configuration/setup/Setup.go
index ee49c45..7cd71df 100644
--- a/internal/configuration/setup/Setup.go
+++ b/internal/configuration/setup/Setup.go
@@ -23,8 +23,11 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"os"
+	"runtime"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 )
 
@@ -121,6 +124,9 @@ func startSetupWebserver() {
 	fmt.Println("Please open http://" + resolveHostIp() + ":" + port + "/setup to setup Gokapi.")
 	listener, err := net.Listen("tcp", ":"+port)
 	if err != nil {
+		if isErrorAddressAlreadyInUse(err) {
+			fmt.Println("This port is already in use. Use parameter -p or env variable GOKAPI_PORT to change the port.")
+		}
 		log.Fatalf("Setup Webserver: %v", err)
 	}
 	if statusChannel != nil {
@@ -139,6 +145,25 @@ func startSetupWebserver() {
 	}
 }
 
+func isErrorAddressAlreadyInUse(err error) bool {
+	var eOsSyscall *os.SyscallError
+	if !errors.As(err, &eOsSyscall) {
+		return false
+	}
+	var errErrno syscall.Errno
+	if !errors.As(eOsSyscall, &errErrno) {
+		return false
+	}
+	if errErrno == syscall.EADDRINUSE {
+		return true
+	}
+	const WSAEADDRINUSE = 10048
+	if runtime.GOOS == "windows" && errErrno == WSAEADDRINUSE {
+		return true
+	}
+	return false
+}
+
 func resolveHostIp() string {
 	netInterfaceAddresses, err := net.InterfaceAddrs()
 	if err != nil {
diff --git a/internal/environment/flagparser/FlagParser_test.go b/internal/environment/flagparser/FlagParser_test.go
deleted file mode 100644
index dba4dc2..0000000
--- a/internal/environment/flagparser/FlagParser_test.go
+++ /dev/null
@@ -1 +0,0 @@
-package flagparser
diff --git a/internal/models/End2EndEncryption_test.go b/internal/models/End2EndEncryption_test.go
new file mode 100644
index 0000000..a8e6b63
--- /dev/null
+++ b/internal/models/End2EndEncryption_test.go
@@ -0,0 +1,36 @@
+package models
+
+import "testing"
+
+func TestE2EInfoEncrypted_HasBeenSetUp(t *testing.T) {
+	type fields struct {
+		Version        int
+		Nonce          []byte
+		Content        []byte
+		AvailableFiles []string
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   bool
+	}{
+		{"empty", fields{}, false},
+		{"version 0", fields{Version: 0}, false},
+		{"version 1, empty", fields{Version: 1}, false},
+		{"version 0, not empty", fields{Version: 0, Content: []byte("content")}, false},
+		{"version 1, not empty", fields{Version: 1, Content: []byte("content")}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &E2EInfoEncrypted{
+				Version:        tt.fields.Version,
+				Nonce:          tt.fields.Nonce,
+				Content:        tt.fields.Content,
+				AvailableFiles: tt.fields.AvailableFiles,
+			}
+			if got := e.HasBeenSetUp(); got != tt.want {
+				t.Errorf("HasBeenSetUp() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}