diff --git a/src/main/java/com/example/g8backend/controller/TrackerController.java b/src/main/java/com/example/g8backend/controller/TrackerController.java
index 1511c76..4e26abb 100644
--- a/src/main/java/com/example/g8backend/controller/TrackerController.java
+++ b/src/main/java/com/example/g8backend/controller/TrackerController.java
@@ -1,7 +1,9 @@
 package com.example.g8backend.controller;
 
+import com.example.g8backend.dto.AnnounceRequestDTO;
+import com.example.g8backend.dto.AnnounceResponseDTO;
+import jakarta.servlet.http.HttpServletRequest;
 import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 import com.example.g8backend.service.ITrackerService;
@@ -13,21 +15,41 @@
     @Autowired
     private ITrackerService trackerService;
 
-    @Autowired
-    private RedisTemplate<String, Object> redisTemplate;
-
     @GetMapping("/announce/{passkey}")
-    public ResponseEntity<?> getAnnouncements(
-            @RequestParam(name = "info_hash") String infoHash,
-            @RequestParam(name = "peer_id") String peerId,
-            @RequestParam(name = "port") int port,
-            @RequestParam(name = "uploaded") long uploaded,
-            @RequestParam(name = "downloaded") long downloaded,
-            @RequestParam(name = "left") long left,
-            @RequestParam(name = "compact", required = false) int compact,
-            @RequestParam(name = "event", required = false) String event,
+    public ResponseEntity<AnnounceResponseDTO> getAnnouncements(
+            HttpServletRequest request,
+            @RequestParam("info_hash") String infoHash,
+            @RequestParam("peer_id") String peerId,
+            @RequestParam("port") int port,
+            @RequestParam("uploaded") double uploaded,
+            @RequestParam("downloaded") double downloaded,
+            @RequestParam(value = "event", required = false) String event,
+            @RequestParam(value = "left", required = false) Double left,
+            @RequestParam(value = "compact", required = false) Integer compact,
             @PathVariable String passkey) {
 
-        return null;
+        AnnounceRequestDTO requestDTO = new AnnounceRequestDTO();
+        requestDTO.setPasskey(passkey);
+        requestDTO.setInfoHash(infoHash);
+        requestDTO.setPeerId(peerId);
+        requestDTO.setPort(port);
+        requestDTO.setUploaded(uploaded);
+        requestDTO.setDownloaded(downloaded);
+        requestDTO.setEvent(event);
+        requestDTO.setLeft(left);
+        requestDTO.setCompact(compact);
+
+        String ipAddress = request.getHeader("X-Forwarded-For");
+        if (ipAddress == null || ipAddress.isEmpty() || "unknown".equalsIgnoreCase(ipAddress)) {
+            ipAddress = request.getHeader("Proxy-Client-IP");
+        }
+        if (ipAddress == null || ipAddress.isEmpty() || "unknown".equalsIgnoreCase(ipAddress)) {
+            ipAddress = request.getHeader("WL-Proxy-Client-IP");
+        }
+        if (ipAddress == null || ipAddress.isEmpty() || "unknown".equalsIgnoreCase(ipAddress)) {
+            ipAddress = request.getRemoteAddr();
+        }
+        requestDTO.setIp(ipAddress.split(",")[0]);
+        return ResponseEntity.ok(trackerService.handleAnnounce(requestDTO));
     }
 }
diff --git a/src/main/java/com/example/g8backend/dto/AnnounceRequestDTO.java b/src/main/java/com/example/g8backend/dto/AnnounceRequestDTO.java
new file mode 100644
index 0000000..e54f06d
--- /dev/null
+++ b/src/main/java/com/example/g8backend/dto/AnnounceRequestDTO.java
@@ -0,0 +1,17 @@
+package com.example.g8backend.dto;
+
+import lombok.Data;
+
+@Data
+public class AnnounceRequestDTO {
+    private String passkey;
+    private String infoHash;
+    private String peerId;
+    private int port;
+    private double uploaded;
+    private double downloaded;
+    private double left;
+    private Integer compact; // 可选
+    private String event;    // 可选
+    private String ip;
+}
diff --git a/src/main/java/com/example/g8backend/dto/AnnounceResponseDTO.java b/src/main/java/com/example/g8backend/dto/AnnounceResponseDTO.java
new file mode 100644
index 0000000..bbb1dc8
--- /dev/null
+++ b/src/main/java/com/example/g8backend/dto/AnnounceResponseDTO.java
@@ -0,0 +1,16 @@
+package com.example.g8backend.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.util.List;
+import java.util.Map;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class AnnounceResponseDTO {
+    private int interval;
+    private List<Map<String, Object>> peers;
+}
diff --git a/src/main/java/com/example/g8backend/entity/Peer.java b/src/main/java/com/example/g8backend/entity/Peer.java
index b59f7ee..e3e1342 100644
--- a/src/main/java/com/example/g8backend/entity/Peer.java
+++ b/src/main/java/com/example/g8backend/entity/Peer.java
@@ -6,7 +6,7 @@
 @Data
 @TableName("peers")
 public class Peer {
-    private Long peerId;
+    private String peerId;
     private String info_hash;
     private String passkey;
     private String ipAddress;
diff --git a/src/main/java/com/example/g8backend/mapper/PeerMapper.java b/src/main/java/com/example/g8backend/mapper/PeerMapper.java
index ce84bbe..f0b9b85 100644
--- a/src/main/java/com/example/g8backend/mapper/PeerMapper.java
+++ b/src/main/java/com/example/g8backend/mapper/PeerMapper.java
@@ -2,7 +2,14 @@
 
 import com.baomidou.mybatisplus.core.mapper.BaseMapper;
 import com.example.g8backend.entity.Peer;
+import org.apache.ibatis.annotations.Mapper;
 
+import java.util.List;
+
+@Mapper
 public interface PeerMapper extends BaseMapper<Peer> {
-
+    // get peer by primary key(peerId, infoHash, passkey)
+    Peer getPeerByPK(String peerId, String infoHash, String passkey);
+    List<Peer> getPeerByInfoHashAndPeerId(String infoHash, String peerId);
+    void updatePeer(String passkey, String peerId, String info_hash, double uploaded, double downloaded);
 }
diff --git a/src/main/java/com/example/g8backend/service/ITrackerService.java b/src/main/java/com/example/g8backend/service/ITrackerService.java
index e522d77..055e317 100644
--- a/src/main/java/com/example/g8backend/service/ITrackerService.java
+++ b/src/main/java/com/example/g8backend/service/ITrackerService.java
@@ -1,6 +1,9 @@
 package com.example.g8backend.service;
 
 
-public interface ITrackerService {
+import com.example.g8backend.dto.AnnounceRequestDTO;
+import com.example.g8backend.dto.AnnounceResponseDTO;
 
+public interface ITrackerService {
+    AnnounceResponseDTO handleAnnounce(AnnounceRequestDTO requestDTO);
 }
diff --git a/src/main/java/com/example/g8backend/service/impl/TorrentServiceImpl.java b/src/main/java/com/example/g8backend/service/impl/TorrentServiceImpl.java
index bedb94a..199ff2a 100644
--- a/src/main/java/com/example/g8backend/service/impl/TorrentServiceImpl.java
+++ b/src/main/java/com/example/g8backend/service/impl/TorrentServiceImpl.java
@@ -17,7 +17,7 @@
     @Resource
     private TorrentMapper torrentMapper;
 
-    String tracker = "http://127.0.0.1:8080/announce/";
+    String tracker = "http://127.0.0.1:8080/tracker/announce/";
 
     @Override
     public Torrent handleTorrentUpload(File file, Long userId, String passkey) throws IOException, IllegalArgumentException {
diff --git a/src/main/java/com/example/g8backend/service/impl/TrackerServiceImpl.java b/src/main/java/com/example/g8backend/service/impl/TrackerServiceImpl.java
index c0dba70..ffb5e65 100644
--- a/src/main/java/com/example/g8backend/service/impl/TrackerServiceImpl.java
+++ b/src/main/java/com/example/g8backend/service/impl/TrackerServiceImpl.java
@@ -1,8 +1,88 @@
 package com.example.g8backend.service.impl;
 
+import com.example.g8backend.dto.AnnounceRequestDTO;
+import com.example.g8backend.dto.AnnounceResponseDTO;
+import com.example.g8backend.entity.Peer;
+import com.example.g8backend.mapper.PeerMapper;
 import com.example.g8backend.service.ITrackerService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.stereotype.Service;
 
+import java.util.*;
+
 @Service
 public class TrackerServiceImpl implements ITrackerService {
+    final int interval = 30;
+
+    @Autowired
+    private PeerMapper peerMapper;
+
+    @Autowired
+    private RedisTemplate<String, Object> redisTemplate;
+
+    @Override
+    public AnnounceResponseDTO handleAnnounce(AnnounceRequestDTO requestDTO) {
+        String passkey = requestDTO.getPasskey();
+        String infoHash = requestDTO.getInfoHash();
+        String peerId = requestDTO.getPeerId();
+        int port = requestDTO.getPort();
+        String ip = requestDTO.getIp();
+        double uploaded = requestDTO.getUploaded();
+        double downloaded = requestDTO.getDownloaded();
+        String event = requestDTO.getEvent();
+
+        String redisKey = "peers:" + infoHash;
+
+        if ("stopped".equalsIgnoreCase(event)) {
+            // 从 Redis 中移除 peer
+            redisTemplate.opsForSet().remove(redisKey, peerId);
+            return new AnnounceResponseDTO(interval, Collections.emptyList());
+        }
+
+        // 插入或更新 peer 信息
+        Peer existingPeer = peerMapper.getPeerByPK(peerId, infoHash, passkey);
+        if (existingPeer == null) {
+            Peer newPeer = new Peer();
+            newPeer.setPeerId(peerId);
+            newPeer.setInfo_hash(infoHash);
+            newPeer.setPasskey(passkey);
+            newPeer.setIpAddress(ip); // TODO: 从 request 获取真实 IP
+            newPeer.setPort(port);
+            newPeer.setUploaded(uploaded);
+            newPeer.setDownloaded(downloaded);
+            peerMapper.insert(newPeer);
+        } else {
+            existingPeer.setUploaded(uploaded);
+            existingPeer.setDownloaded(downloaded);
+            peerMapper.updatePeer(existingPeer.getPasskey(), existingPeer.getPeerId(), existingPeer.getInfo_hash(),
+                    existingPeer.getUploaded(), existingPeer.getDownloaded());
+        }
+
+        // 缓存 peer 到 Redis
+        redisTemplate.opsForSet().add(redisKey, peerId);
+
+        // 构造返回 peer 列表
+        List<Map<String, Object>> peerList = new ArrayList<>();
+        Set<Object> peerIds = redisTemplate.opsForSet().members(redisKey);
+        try {
+            assert peerIds != null;
+            for (Object pid : peerIds) {
+                List<Peer> peers = peerMapper.getPeerByInfoHashAndPeerId(infoHash, (String) pid);
+                for (Peer peer : peers) {
+                    if (peer != null) {
+                        Map<String, Object> peerMap = new HashMap<>();
+                        peerMap.put("ip", peer.getIpAddress());
+                        peerMap.put("port", peer.getPort());
+                        peerList.add(peerMap);
+                    }
+                }
+            }
+        } catch (Exception e) {
+            return new AnnounceResponseDTO(interval, Collections.emptyList());
+        }
+
+        return new AnnounceResponseDTO(interval, peerList);
+    }
+
 }
diff --git a/src/main/java/com/example/g8backend/util/TorrentUtil.java b/src/main/java/com/example/g8backend/util/TorrentUtil.java
index e8360bc..b7390d6 100644
--- a/src/main/java/com/example/g8backend/util/TorrentUtil.java
+++ b/src/main/java/com/example/g8backend/util/TorrentUtil.java
@@ -4,12 +4,13 @@
 import com.dampcake.bencode.Type;
 
 import java.io.*;
+import java.nio.charset.StandardCharsets;
 import java.security.MessageDigest;
 import java.util.Map;
 
 public class TorrentUtil {
 
-    private static final Bencode bencode = new Bencode();
+    private static final Bencode bencode = new Bencode(StandardCharsets.ISO_8859_1);
 
     public static byte[] injectTracker(File torrentFile, String trackerUrl) throws IOException {
         byte[] fileBytes = readBytes(torrentFile);
@@ -17,7 +18,9 @@
         Map<String, Object> torrentMap = bencode.decode(fileBytes, Type.DICTIONARY);
 
         // trackerUrl: ip:port + /announce / {passkey}
-        torrentMap.put("announce", trackerUrl);
+        byte[] ISO_trackerUrlByte = trackerUrl.getBytes(StandardCharsets.ISO_8859_1);
+        String ISO_trackerUrl = new String(ISO_trackerUrlByte, StandardCharsets.ISO_8859_1);
+        torrentMap.put("announce", ISO_trackerUrl); // ISO-8859-1
 
         return bencode.encode(torrentMap);
     }
diff --git a/src/main/resources/application.properties b/src/main/resources/application.properties
index 7f85f87..22f3728 100644
--- a/src/main/resources/application.properties
+++ b/src/main/resources/application.properties
@@ -18,3 +18,5 @@
 spring.mail.properties.mail.smtp.auth=true
 spring.mail.properties.mail.smtp.ssl.enable=true
 spring.mail.properties.mail.smtp.socketFactory.class=javax.net.ssl.SSLSocketFactory
+
+logging.level.org.springframework.data.redis= DEBUG
diff --git a/src/main/resources/mapper/PeerMapper.xml b/src/main/resources/mapper/PeerMapper.xml
new file mode 100644
index 0000000..b3d4780
--- /dev/null
+++ b/src/main/resources/mapper/PeerMapper.xml
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
+        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
+<mapper namespace="com.example.g8backend.mapper.PeerMapper">
+    <select id="getPeerByPK">
+        SELECT * FROM peers
+        WHERE peer_id = #{peerId} and info_hash = #{infoHash} and passkey = #{passkey}
+    </select>
+    <select id="getPeerByInfoHashAndPeerId">
+        SELECT * FROM peers
+        WHERE info_hash = #{infoHash} and peer_id = #{peerId}
+    </select>
+    <update id="updatePeer">
+        UPDATE peers
+        SET uploaded = #{uploaded}, downloaded = #{downloaded}
+        WHERE peer_id = #{peerId} and info_hash = #{info_hash} and passkey = #{passkey}
+    </update>
+</mapper>
diff --git a/src/test/java/com/example/g8backend/service/TrackerServiceTest.java b/src/test/java/com/example/g8backend/service/TrackerServiceTest.java
new file mode 100644
index 0000000..829fe15
--- /dev/null
+++ b/src/test/java/com/example/g8backend/service/TrackerServiceTest.java
@@ -0,0 +1,138 @@
+package com.example.g8backend.service;
+
+import com.example.g8backend.dto.AnnounceRequestDTO;
+import com.example.g8backend.dto.AnnounceResponseDTO;
+import com.example.g8backend.entity.Peer;
+import com.example.g8backend.mapper.PeerMapper;
+import com.example.g8backend.service.impl.TrackerServiceImpl;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.*;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.core.SetOperations;
+
+import java.util.*;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.*;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+public class TrackerServiceTest {
+
+    @InjectMocks
+    private TrackerServiceImpl trackerService;
+
+    @Mock
+    private PeerMapper peerMapper;
+
+    @Mock
+    private RedisTemplate<String, Object> redisTemplate;
+
+    @Mock
+    private SetOperations<String, Object> setOperations;
+
+    @BeforeEach
+    public void setUp() {
+        when(redisTemplate.opsForSet()).thenReturn(setOperations);
+    }
+
+    @Test
+    public void testHandleAnnounceStoppedEvent() {
+        AnnounceRequestDTO requestDTO = new AnnounceRequestDTO();
+        requestDTO.setEvent("stopped");
+        requestDTO.setInfoHash("infohash");
+        requestDTO.setPeerId("peer1");
+
+        AnnounceResponseDTO response = trackerService.handleAnnounce(requestDTO);
+
+        verify(setOperations).remove("peers:infohash", "peer1");
+        assertEquals(30, response.getInterval());
+        assertTrue(response.getPeers().isEmpty());
+    }
+
+    @Test
+    public void testHandleAnnounceWithNewPeer() {
+        AnnounceRequestDTO requestDTO = new AnnounceRequestDTO();
+        requestDTO.setPasskey("key123");
+        requestDTO.setInfoHash("infohash");
+        requestDTO.setPeerId("peer1");
+        requestDTO.setIp("192.168.0.1");
+        requestDTO.setPort(6881);
+        requestDTO.setUploaded(1000);
+        requestDTO.setDownloaded(500);
+        requestDTO.setEvent("started");
+
+        when(peerMapper.getPeerByPK("peer1", "infohash", "key123")).thenReturn(null);
+        when(setOperations.members("peers:infohash")).thenReturn(Set.of("peer1"));
+        when(peerMapper.getPeerByInfoHashAndPeerId("infohash", "peer1")).thenReturn(List.of(new Peer() {{
+            setIpAddress("192.168.0.1");
+            setPort(6881);
+        }}));
+
+        AnnounceResponseDTO response = trackerService.handleAnnounce(requestDTO);
+
+        verify(peerMapper).insert(any(Peer.class));
+        verify(setOperations).add("peers:infohash", "peer1");
+        assertEquals(30, response.getInterval());
+        assertEquals(1, response.getPeers().size());
+        assertEquals("192.168.0.1", response.getPeers().get(0).get("ip"));
+    }
+
+    @Test
+    public void testHandleAnnounceWithExistingPeer() {
+        AnnounceRequestDTO requestDTO = new AnnounceRequestDTO();
+        requestDTO.setPasskey("key123");
+        requestDTO.setInfoHash("infohash");
+        requestDTO.setPeerId("peer2");
+        requestDTO.setIp("192.168.1.1");
+        requestDTO.setPort(6882);
+        requestDTO.setUploaded(2000);
+        requestDTO.setDownloaded(1000);
+        requestDTO.setEvent("update");
+
+        Peer existing = new Peer();
+        existing.setPeerId("peer2");
+        existing.setPasskey("key123");
+        existing.setInfo_hash("infohash");
+        existing.setUploaded(1000.0);
+        existing.setDownloaded(500.0);
+
+        when(peerMapper.getPeerByPK("peer2", "infohash", "key123")).thenReturn(existing);
+        when(setOperations.members("peers:infohash")).thenReturn(Set.of("peer2"));
+        when(peerMapper.getPeerByInfoHashAndPeerId("infohash", "peer2")).thenReturn(List.of(new Peer() {{
+            setIpAddress("192.168.1.1");
+            setPort(6882);
+        }}));
+
+        AnnounceResponseDTO response = trackerService.handleAnnounce(requestDTO);
+
+        verify(peerMapper).updatePeer(eq("key123"), eq("peer2"), eq("infohash"), eq(2000.0), eq(1000.0));
+        verify(setOperations).add("peers:infohash", "peer2");
+        assertEquals(1, response.getPeers().size());
+        assertEquals("192.168.1.1", response.getPeers().get(0).get("ip"));
+    }
+
+    @Test
+    public void testHandleAnnounceExceptionInRedis() {
+        AnnounceRequestDTO requestDTO = new AnnounceRequestDTO();
+        requestDTO.setPasskey("keyX");
+        requestDTO.setInfoHash("hashX");
+        requestDTO.setPeerId("peerX");
+        requestDTO.setIp("10.0.0.1");
+        requestDTO.setPort(6883);
+        requestDTO.setUploaded(100);
+        requestDTO.setDownloaded(200);
+        requestDTO.setEvent("started");
+
+        when(peerMapper.getPeerByPK(any(), any(), any())).thenReturn(null);
+        when(setOperations.members(anyString())).thenReturn(new HashSet<>() );
+
+        AnnounceResponseDTO response = trackerService.handleAnnounce(requestDTO);
+
+        assertEquals(30, response.getInterval());
+        assertTrue(response.getPeers().isEmpty());
+    }
+}
diff --git a/uploaded-torrents/upload-1263176031835183570.torrent b/uploaded-torrents/upload-1263176031835183570.torrent
deleted file mode 100644
index 8634e79..0000000
--- a/uploaded-torrents/upload-1263176031835183570.torrent
+++ /dev/null
Binary files differ