From 74bf67a9b2a0845af49b6df98f5e2acb519a1b67 Mon Sep 17 00:00:00 2001
From: Gyubin Han <hangyub@gyu.be>
Date: Thu, 1 Jan 2026 02:55:28 +0900
Subject: [PATCH] =?UTF-8?q?Feat:=20=ED=8C=8C=EC=9D=BC=20=EC=A0=84=EC=86=A1?=
 =?UTF-8?q?=20=EA=B8=B0=EB=8A=A5=20=EA=B5=AC=ED=98=84=20(=EC=97=85?=
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- RETR 명령어 구현: 파일 다운로드
  * 파일 존재 여부 확인
  * 데이터 연결을 통한 파일 스트림 전송
  * 전송 바이트 수 로깅
  * 에러 처리 및 연결 자동 종료
- STOR 명령어 구현: 파일 업로드
  * 현재 디렉토리에 파일 생성
  * 데이터 연결을 통한 파일 스트림 수신
  * 전송 완료 후 파일 크기 확인
  * 에러 처리 및 연결 자동 종료
- 두 명령어 모두 PASV 선행 필수
- FileInputStream/FileOutputStream을 사용한 스트림 처리
- 전송 성공/실패에 따른 적절한 응답 코드 반환

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
---
 .../be/gyu/android/server/ftp/FTPSession.java | 104 ++++++++++++++++++
 1 file changed, 104 insertions(+)

diff --git a/app/src/main/java/be/gyu/android/server/ftp/FTPSession.java b/app/src/main/java/be/gyu/android/server/ftp/FTPSession.java
index 5729f64..b725115 100644
--- a/app/src/main/java/be/gyu/android/server/ftp/FTPSession.java
+++ b/app/src/main/java/be/gyu/android/server/ftp/FTPSession.java
@@ -107,6 +107,12 @@ public class FTPSession implements Runnable {
             case "PASV":
                 handlePasv();
                 break;
+            case "RETR":
+                handleRetr(argument);
+                break;
+            case "STOR":
+                handleStor(argument);
+                break;
             case "NOOP":
                 handleNoop();
                 break;
@@ -369,6 +375,104 @@ public class FTPSession implements Runnable {
         }
     }
 
+    private void handleRetr(String fileName) throws IOException {
+        if (!isAuthenticated) {
+            sendResponse(FTPResponse.NOT_LOGGED_IN, "Please login first");
+            return;
+        }
+
+        if (fileName.isEmpty()) {
+            sendResponse(FTPResponse.SYNTAX_ERROR_PARAMETERS, "No file name specified");
+            return;
+        }
+
+        if (dataConnection == null) {
+            sendResponse(FTPResponse.CANNOT_OPEN_DATA_CONNECTION, "Use PASV first");
+            return;
+        }
+
+        java.io.File file = fileSystem.getFile(fileName);
+        if (file == null || !file.exists() || !file.isFile()) {
+            sendResponse(FTPResponse.FILE_UNAVAILABLE, "File not found");
+            dataConnection.close();
+            dataConnection = null;
+            return;
+        }
+
+        sendResponse(FTPResponse.FILE_STATUS_OK, "Opening data connection for " + fileName + " (" + file.length() + " bytes)");
+
+        if (dataConnection.acceptConnection()) {
+            try {
+                java.io.FileInputStream fis = new java.io.FileInputStream(file);
+                if (dataConnection.transferStream(fis)) {
+                    fis.close();
+                    dataConnection.close();
+                    sendResponse(FTPResponse.CLOSING_DATA_CONNECTION, "Transfer complete");
+                    Log.i(TAG, "File sent: " + fileName + " (" + file.length() + " bytes)");
+                } else {
+                    fis.close();
+                    dataConnection.close();
+                    sendResponse(FTPResponse.CONNECTION_CLOSED, "Transfer failed");
+                }
+            } catch (Exception e) {
+                Log.e(TAG, "Error sending file: " + e.getMessage());
+                dataConnection.close();
+                sendResponse(FTPResponse.CONNECTION_CLOSED, "Transfer error: " + e.getMessage());
+            }
+        } else {
+            dataConnection.close();
+            sendResponse(FTPResponse.CANNOT_OPEN_DATA_CONNECTION, "Cannot open data connection");
+        }
+
+        dataConnection = null;
+    }
+
+    private void handleStor(String fileName) throws IOException {
+        if (!isAuthenticated) {
+            sendResponse(FTPResponse.NOT_LOGGED_IN, "Please login first");
+            return;
+        }
+
+        if (fileName.isEmpty()) {
+            sendResponse(FTPResponse.SYNTAX_ERROR_PARAMETERS, "No file name specified");
+            return;
+        }
+
+        if (dataConnection == null) {
+            sendResponse(FTPResponse.CANNOT_OPEN_DATA_CONNECTION, "Use PASV first");
+            return;
+        }
+
+        java.io.File file = new java.io.File(fileSystem.getCurrentDirectory(), fileName);
+
+        sendResponse(FTPResponse.FILE_STATUS_OK, "Opening data connection for " + fileName);
+
+        if (dataConnection.acceptConnection()) {
+            try {
+                java.io.FileOutputStream fos = new java.io.FileOutputStream(file);
+                if (dataConnection.receiveStream(fos)) {
+                    fos.close();
+                    dataConnection.close();
+                    sendResponse(FTPResponse.CLOSING_DATA_CONNECTION, "Transfer complete");
+                    Log.i(TAG, "File received: " + fileName + " (" + file.length() + " bytes)");
+                } else {
+                    fos.close();
+                    dataConnection.close();
+                    sendResponse(FTPResponse.CONNECTION_CLOSED, "Transfer failed");
+                }
+            } catch (Exception e) {
+                Log.e(TAG, "Error receiving file: " + e.getMessage());
+                dataConnection.close();
+                sendResponse(FTPResponse.CONNECTION_CLOSED, "Transfer error: " + e.getMessage());
+            }
+        } else {
+            dataConnection.close();
+            sendResponse(FTPResponse.CANNOT_OPEN_DATA_CONNECTION, "Cannot open data connection");
+        }
+
+        dataConnection = null;
+    }
+
     private void handleNoop() throws IOException {
         sendResponse(FTPResponse.COMMAND_OK, "OK");
     }