Java实现C/S结构的FTP点对点传输文件，写成了服务端和客户端的形式：先来看Server端的代码是如何写的：
01packageftp2;
02importjava.io.*;
.*;
04publicclassServerFTP {
05intport=8083;
06String filepath="D:\\123.txt";
07voidstart(){
08Socket s=null;
09try{
10ServerSocket ss=newServerSocket(port);
11while(true){
12File file=newFile(filepath);
13if(!file.exists()){
14file.createNewFile();
15}
16System.out.println("文件长度："+(int)file.length());
17s=ss.accept();
18System.out.println("建立socket连接");
19DataInputStream dis=newDataInputStream(newBufferedInputStream(newFileInputStream(filepath)));
20DataOutputStream dos=newDataOutputStream(s.getOutputStream());
21dos.writeUTF(file.getName());
22dos.writeLong((long)file.length());
23intbufferSize=8192;
24byte[] buf=newbyte[bufferSize];
25while(true){
26intread=0;
27if(dis!=null){
28read=dis.read(buf);
29}
30if(read==-1){
31break;
32}
33dos.write(buf,0,read);
34}
35dis.close();
36s.close();
37System.out.println("文件传输完毕！！");
38}
39}catch(Exception e) {
40e.printStackTrace();
41}
42}
43publicstaticvoidmain(String[] args) {
44newServerFTP().start();
45}
46}
再来看下Client客户端文件的代码：
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01packageftp2;
02importjava.io.*;
.*;
04publicclassClientFTP {
05privateSocket s=null;
06privateString ip="localhost";
07privateintport=8082;
08publicClientFTP() {
09creationConnection();
10}
11privatevoidcreationConnection() {
12try{
13s=newSocket(ip,port);
14}catch(Exception e) {
15// TODO: handle exception
16}
17}
18privatevoidgetFile() {
19String savePath="I:\\";
20intbufferSize=8193;
21byte[] buf=newbyte[bufferSize];
22intpassedlen=0;
23longlength=0;
24try{
25DataInputStream dis=newDataInputStream(newBufferedInputStream(s.getInputStream()));
26savePath+=dis.readUTF();
27DataOutputStream dos=newDataOutputStream(newBufferedOutputStream(newFileOutputStream(savePath)));
28length=dis.readLong();
29System.out.println("文件长度："+length+"\n");
30while(true) {
31intread=0;
32if(dis!=null){
33read=dis.read(buf);
34}
35passedlen+=read;
36if(read==-1) {
37break;
38}
39dos.write(buf,0,read);
40}
41System.out.println("接收文件另存为："+savePath+"\n");
42dos.close();
43}catch(Exception e) {
44// TODO: handle exception
45}
46}
47publicstaticvoidmain(String[] args) {
48newClientFTP().getFile();
49}
50}
分别将上述两段代码保存为ServerFTP.java、ClientFTP.java，可在编译器中运行生成文件。
