Windows下实现TCP通信

今天我们介绍如何在Windows下实现TCP通信，开发环境是Visual Stdio 2005

我们的程序很简单，客户端发送一个字符串给服务器，服务器返回这个字符串的大写形式，关于如何实现Windows下的UDP通信，请看这里：

http://blog.youkuaiyun.com/htttw/article/details/7596358
server.cpp:

#include <stdio.h>
#include <winsock2.h>

#pragma comment(lib,"ws2_32.lib")


#define SERVER_PORT 9153


void toUpper(char * in, char * out, int len)
{
  int i;
  char diff = 'a' - 'A';
  
  for(i=0; i<len; ++i)
  {
    if( (in[i] >= 'a') && (in[i] <= 'z') )
	{
	  out[i] = in[i] - diff;
	}
	else
	{
      out[i] = in[i];
	}
  }
}


int main()
{
  /* init winsock */
  WSADATA wsaData;
  
  if(WSAStartup(MAKEWORD(2, 1), &wsaData))
  { 
    printf("winsock init failed\n");
    return 1;
  }

  /* create a tcp socket */
  SOCKET serverSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if(serverSock <= 0)
  {
    printf("socket create failed\n");
    return -1;
  }

  SOCKADDR_IN serverAddr;
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_port = htons(SERVER_PORT);            /* 监听端口 */
  serverAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);  /* 本机 */

  if(bind(serverSock, (SOCKADDR *)&serverAddr, sizeof(serverAddr)) != 0)
  {
    printf("bind failed\n");
    return -1;
  }

  /* start listen */
  printf("start listening...\n");
  if(listen(serverSock, 1) != 0)
  {
    printf("listen failed\n");
    return -1;
  }

  int len = sizeof(SOCKADDR_IN);

  /* waiting for connection */
  SOCKADDR_IN clientAddr;
  SOCKET clientSock = accept(serverSock, (SOCKADDR *)&clientAddr, &len);
  if(clientSock <= 0)
  {
    printf("accept failed\n");
    return -1;
  }
  printf("connected\n");

  char bufferIn[1024];
  char bufferOut[1024];
  while(1)
  {
    bufferIn[0] = '\0';

    printf("waiting...\n");

    if(recv(clientSock, bufferIn, sizeof(bufferIn), 0) <= 0)
    {
      /* error occurs */
      printf("close connection\n");
      break;
    }
    printf("got: %s", bufferIn);

	toUpper(bufferIn, bufferOut, len);

    if(send(clientSock, bufferOut, sizeof(bufferOut), 0)<=0)
    {
      printf("send error\n");
      break;
    }
  }

  closesocket(clientSock);

  WSACleanup();

  return 0;
}

client.cpp:

#include <stdio.h>
#include <winsock2.h>

#pragma comment(lib,"ws2_32.lib")


#define SERVER_ADDRESS "127.0.0.1"
#define SERVER_PORT 9153


int main()
{
  /* init winsock */
  WSADATA wsaData;
  
  if(WSAStartup(MAKEWORD(2, 1), &wsaData))
  { 
    printf("winsock init failed\n");
    return 1;
  }

  SOCKADDR_IN serverAddr;
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_port = htons(SERVER_PORT);                      /* 服务器监听端口 */
  serverAddr.sin_addr.S_un.S_addr = inet_addr(SERVER_ADDRESS);     /* 服务器地址 */

  /* connect to server */
  printf("connecting...\n");

  /* create a tcp socket  */
  SOCKET sock_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if(sock_fd <= 0)
  {
    printf("socket create failed\n");
    return -1;
  }

  int len = sizeof(serverAddr);
  if(connect(sock_fd, (SOCKADDR *)&serverAddr, len) != 0)
  {
    printf("connection failed\n");
    return -1;
  }
  printf("connected\n");


  char buffer[1024];
  while(1)
  {
    printf("press: ");
    fgets(buffer, sizeof(buffer), stdin);
    
    /* send to server */
    if(send(sock_fd, buffer, sizeof(buffer), 0) <= 0)
    {
      printf("send error\n");
      break;
    }

    if(recvfrom(sock_fd, buffer, sizeof(buffer), 0, (struct sockaddr *)&serverAddr, &len) != SOCKET_ERROR)
    {
      printf("got: %s", buffer);
    }
  }

  WSACleanup();
  
  return 0;
}

原理不多讲了，具体可以参考http://blog.youkuaiyun.com/htttw/article/details/7519964，虽然是Linux平台的，但原理类似。

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