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TCP SOCKET CLIENT

先撸一个echo server

const debug = require("debug")('app');
const net = require("net");

const port = 12009;

net
  .createServer(socket => {
    debug('>>> client connected');
    socket.on("data", data => {
      debug(`echoing: ${data.toString()}`);
      socket.write(data.toString());
    });
  })
  .listen(port, () => {
    debug(`server started at port ${port}`);
  });

telnet 127.0.0.1 12009, 服务器搞定。

再来看Java如何操作Socket, 这部分和C++/C#大同小异, 直接看代码就行。

this.client = new Socket();
this.client.connect(this.endpoint);
InputStream inputStream = this.client.getInputStream();
OutputStream outputStream = this.client.getOutputStream();

这里的重点在流的读写操作的抽象概念

  • InputStream/OutputStream负责byte读写
  • Reader/Writer负责对Stream进行文本读写

先来看二进制读写,

InputStream

  • available(): Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream.
  • close()
  • read(): Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown. [注] socket下的input stream不存在EOF的情况, 所以不会返回-1, 当available为0, read会block, 所以这个是同步方法.
  • read(byte[] b)
  • read(byte[] b, int off, int len)
  • reset()
  • skip()

直接操作InputStream

InputStream inputStream = this.client.getInputStream();
int len = inputStream.available();
byte[] buffer = new byte[len];
logger.debug("available: {}", len);
int result = inputStream.read(buffer, 0, len+10);
logger.debug("read byte count: {}", result);
logger.debug("body: {}", buffer);
logger.debug("{}", new String(buffer, StandardCharsets.UTF_8));

len = inputStream.available(); // 没有更多数据, 就返回0
logger.debug("now available: {}", len);
inputStream.read(); // BLOCK
logger.debug("WAIT SERVER SEND DATA");

然后可以通过decorator包装扩展对stream操作,

DataInputStream wrappedInputStream = new DataInputStream(new BufferedInputStream(this.client.getInputStream()));

wrappedInputStream.readChar()
wrappedInputStream.readInt()

这个char也有个坑, 一读就是两个byte, 要谨慎, readInt读4个bytes,

public final int readInt() throws IOException {
    int ch1 = in.read();
    int ch2 = in.read();
    int ch3 = in.read();
    int ch4 = in.read();
    if ((ch1 | ch2 | ch3 | ch4) < 0)
        throw new EOFException();
    return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
}

这里采用Big-endian (Java统一都是Big-endian)

0x45679812

Address 00 01 02 03

Little-endian 12 98 67 45 Big-endian 45 67 98 12

OutputStream

  • close()
  • flush()
  • write(int b)
  • write(byte[] b)
  • write(byte[], int off, int len)

异步Socket

到这里都是同步操作, 同步操作就需要开额外thread, 一堆破事, 所以更好的操作肯定是异步.

BIO、NIO、AIO的区别

  • BIO – Blocking IO 即阻塞式IO。
  • NIO – Non-Blocking IO, 即非阻塞式IO或异步IO。
  • AIO - Asynchronous IO, 可以理解为NIO 2.0

BIO 傻, NIO 难用, AIO 没人用 所以Netty就要华丽登场

NETTY

参考阅读: