From 1df338f9b31cb218f288ec6588800b14deb43173 Mon Sep 17 00:00:00 2001
From: MengMengCode <227010654+MengMengCode@users.noreply.github.com>
Date: Tue, 18 Aug 2026 14:45:23 +0800
Subject: [PATCH] FIX #59

---
 internal/device/sms_pdu.go      |  6 ++++++
 internal/device/sms_pdu_test.go | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/internal/device/sms_pdu.go b/internal/device/sms_pdu.go
index ddb3db5..d627b12 100644
--- a/internal/device/sms_pdu.go
+++ b/internal/device/sms_pdu.go
@@ -852,7 +852,13 @@ func decodeUserData(
 		message.Text = string(utf16.Decode(units))
 		return nil
 	default:
+		// 8-bit (binary) user data has no portable text representation, so the
+		// raw payload bytes are rendered as uppercase hexadecimal after the user
+		// data header is stripped. This keeps the bubble non-empty and gives a
+		// faithful rendering of the delivered content rather than a blank "".
 		message.Encoding = SMSEncoding8BitPDU
+		payload := data[headerBytes:]
+		message.Text = strings.ToUpper(hex.EncodeToString(payload))
 		return nil
 	}
 }
diff --git a/internal/device/sms_pdu_test.go b/internal/device/sms_pdu_test.go
index 405f17e..ffb926f 100644
--- a/internal/device/sms_pdu_test.go
+++ b/internal/device/sms_pdu_test.go
@@ -263,3 +263,21 @@ func TestParseCMGLPreservesUndecodableRecord(t *testing.T) {
 		t.Fatalf("messages = %#v", messages)
 	}
 }
+
+func TestDecode8BitPDUShowsHexPayload(t *testing.T) {
+	// SMS-DELIVER with no SMSC, from +12345, DCS=0xF5 (8-bit data,
+	// alphabet bits 0x0c), UDL=3. User data bytes are 0xAA 0xBB 0xCC.
+	// Built from the GSM-7 deliver vector by swapping the DCS to 0xF5
+	// and replacing the user data with three raw binary bytes.
+	message, err := decodeSMSPDU(
+		"000405912143F500F54210203040500003AABBCC",
+	)
+	if err != nil {
+		t.Fatalf("decode 8-bit: %v", err)
+	}
+	if message.Encoding != SMSEncoding8BitPDU ||
+		message.Text != "AABBCC" ||
+		message.RawUserData != "AABBCC" {
+		t.Fatalf("8-bit message = %#v", message)
+	}
+}