【使用java创建TCP连接，让服务端读取200MB的本地文件并发送给客户端，客户端接收文件并保存到本地】

TCP连接发送文件

服务端为java，客户端也为java。（实际场景中客户端和服务端可以为C++）。
使用TCP连接发送文件需要注意：
规定好双方的协议，即发送端要怎么发送，接收端要怎么接收

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一、java服务端

publicclassTCPServer{privatestaticfinalintPORT=8081;privatestaticfinalStringFILE_PATH="C:\\Users\\Wasond\\Desktop\\11.zip";// 待发送的 100MB 文件privatestaticfinallongCHUNK_SIZE=1024*1024;// 1MB 分块publicstaticvoidmain(String[]args){// SpringApplication.run(FileServerApplication.class, args);newThread(()->{try(ServerSocketserverSocket=newServerSocket(PORT)){System.out.println("Server started on port "+PORT);while(true){SocketclientSocket=serverSocket.accept();newThread(()->sendFile(clientSocket)).start();}}catch(IOExceptione){e.printStackTrace();}}).start();}privatestaticvoidsendFile(SocketclientSocket){try(java.io.FileInputStreamfileInputStream=newjava.io.FileInputStream(FILE_PATH);DataOutputStreamout=newDataOutputStream(clientSocket.getOutputStream())){longfileSize=newjava.io.File(FILE_PATH).length();out.writeLong(fileSize);// 先发送文件大小（客户端用于进度计算）byte[]buffer=newbyte[(int)CHUNK_SIZE];intbytesRead;longtransferred=0;while(transferred<fileSize){intchunkSize=(int)Math.min(CHUNK_SIZE,fileSize-transferred);bytesRead=fileInputStream.read(buffer,0,chunkSize);if(bytesRead==-1)break;// 文件读取完毕// 发送分块数据out.writeInt(bytesRead);// 发送当前块实际大小out.write(buffer,0,bytesRead);transferred+=bytesRead;}System.out.println("File sent successfully. Total bytes: "+transferred);}catch(IOExceptione){e.printStackTrace();}finally{try{clientSocket.close();}catch(IOExceptione){e.printStackTrace();}}}}

二、java客户端

importjava.io.*;importjava.net.Socket;publicclassTCPClient{privatestaticfinalStringSERVER_HOST="localhost";privatestaticfinalintSERVER_PORT=8081;privatestaticfinalStringOUTPUT_FILE="C:\\Users\\Wasond\\Desktop\\777.zip";publicstaticvoidmain(String[]args){try(Socketsocket=newSocket(SERVER_HOST,SERVER_PORT);DataInputStreamin=newDataInputStream(socket.getInputStream());FileOutputStreamfos=newFileOutputStream(OUTPUT_FILE)){// 1. 读取文件总大小longfileSize=in.readLong();System.out.println("Receiving file (size: "+fileSize+" bytes)");// 2. 分块接收并写入本地文件longreceived=0;while(received<fileSize){intchunkSize=in.readInt();// 读取当前块大小byte[]buffer=newbyte[chunkSize];// in.readFully(buffer); // 确保读取完整块// 替换 in.readFully(buffer) 为更安全的读取方式intbytesRead=0;while(bytesRead<chunkSize){intresult=in.read(buffer,bytesRead,chunkSize-bytesRead);if(result==-1){thrownewIOException("Unexpected end of stream");}bytesRead+=result;}fos.write(buffer);received+=chunkSize;// 打印进度（可选）System.out.printf("Progress: %.2f%%\n",(received*100.0/fileSize));}System.out.println("File received and saved to "+OUTPUT_FILE);}catch(IOExceptione){e.printStackTrace();}}}

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