Tcp

基于连接的Tcp编程.

 

代码注释，如下：

#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib,"WS2_32.lib")

#define BUF_SIZE 64

int main()
{
    WSADATA wsadata; //包含DLL期望程序使用的版本和支持的最高版本等字段
    int retVal;

    SOCKET sServer;
    SOCKET sClient;
    char buf[BUF_SIZE];

    //
    retVal=WSAStartup(MAKEWORD(2,2),&wsadata);
    if(retVal != 0)
    {
        printf("WSAStartup failed!\n");
    }

    //创建套接字
    sServer=socket(AF_INET,SOCK_STREAM,IPPROTO_IP);
    if(sServer == INVALID_SOCKET)
    {
        printf("socket failed!\n");

        WSACleanup();
        return -1;
    }

    //绑定套接字
    SOCKADDR_IN addrServ;
    addrServ.sin_family=AF_INET; //套接字属于协议族TCP/IP
    addrServ.sin_port=htons(4999);
    addrServ.sin_addr.S_un.S_addr=INADDR_ANY;

    retVal=bind(sServer,(LPSOCKADDR)&addrServ,sizeof(SOCKADDR_IN));
    if(retVal == SOCKET_ERROR)
    {
        printf("bind failed!\n");

        closesocket(sServer);
        WSACleanup();
        return -1;
    }

    //
    retVal=listen(sServer,1);
    if(retVal == SOCKET_ERROR)
    {
        printf("listen failed!\n");

        closesocket(sServer);
        WSACleanup();
        return -1;
    }

    //等待客户端的连接请求
    SOCKADDR_IN addrClient;
    int len=sizeof(SOCKADDR_IN);

    sClient=accept(sServer,(LPSOCKADDR)&addrClient,&len); //返回一个新的套接字句柄
    if(sClient == INVALID_SOCKET)
    {
        printf("accept failed!\n");

        closesocket(sServer);
        WSACleanup();
        return -1;
    }

    //接收数据
    ZeroMemory(buf,BUF_SIZE);

    retVal=recv(sClient,buf,BUF_SIZE,0);
    if(retVal == SOCKET_ERROR)
    {
        printf("recv failed!\n");

        closesocket(sClient);
        closesocket(sServer);
        WSACleanup();
        return -1;
    }

    //
    printf("Server receives data: ");
    printf("%s\n",buf);

    //
    closesocket(sClient);
    closesocket(sServer);
    WSACleanup();
    return 0;
}

 

//Client.cpp
#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib,"WS2_32.lib")

#define BUF_SIZE 64

int main()
{
    WSADATA wsadata;
    int retVal;

    SOCKET sClient;
    char buf[BUF_SIZE];


    //加载套接字DLL
    retVal=WSAStartup(MAKEWORD(2,2),&wsadata);
    if(retVal != 0)
    {
        printf("WSAStartup failed!\n");
    }

    //创建套接字
    sClient=socket(AF_INET,SOCK_STREAM,IPPROTO_IP);
    if(sClient == INVALID_SOCKET)
    {
        printf("socket failed!\n");

        WSACleanup();
        return -1;
    }

    //
    SOCKADDR_IN addrServ;
    addrServ.sin_family=AF_INET; //套接字属于协议族TCP/IP
    addrServ.sin_port=htons(4999);
    addrServ.sin_addr.S_un.S_addr=inet_addr("127.0.0.1");

    retVal=connect(sClient,(LPSOCKADDR)&addrServ,sizeof(SOCKADDR_IN));
    if(retVal == SOCKET_ERROR)
    {
        printf("connect failed!\n");

        closesocket(sClient);
        WSACleanup();
        return -1;
    }

    //发送数据
    ZeroMemory(buf,BUF_SIZE);
    strcpy(buf,"Hello Tcp!");

    retVal=send(sClient,buf,BUF_SIZE,0);
    if(retVal == SOCKET_ERROR)
    {
        printf("send failed!\n");

        closesocket(sClient);
        WSACleanup();
        return -1;
    }

    //
    closesocket(sClient);
    WSACleanup();
    return 0;
}

函数原型：

1.

typedef struct sockaddr_in SOCKADDR_IN;
typedef struct sockaddr_in *PSOCKADDR_IN;
typedef struct sockaddr_in FAR *LPSOCKADDR_IN;

typedef struct sockaddr SOCKADDR;
typedef struct sockaddr *PSOCKADDR;
typedef struct sockaddr FAR *LPSOCKADDR;

 

struct sockaddr_in{
  short sin_family;
  unsigned short sin_port;
  IN_ADDR sin_addr;
  char sin_zero[8];
};

short sin_family; //AF_INET，代表TCP/IP协议族

char sin_zero[8]; //填充大小和SOCKADDR结构一样(16Byetes)

 

typedef struct in_addr {
  union {
    struct {
      u_char s_b1,s_b2,s_b3,s_b4;
    } S_un_b;
    struct {
      u_short s_w1,s_w2;
    } S_un_w;
    u_long S_addr;
  } S_un;
} in_addr;

 

struct sockaddr {
  u_short sa_family;
  char sa_data[14];
};

注：1.SOCKADDR更通用，SOCKADDR_IN针对TCP/IP协议族；2.SOCKADDR_IN弥补了SOCKADDR的地址和端口没有分开的缺陷；3.SOCKADDR_IN用于定义，SOCKADDR用于函数的参数.

2.

 

SOCKET accept(
  SOCKET s,
  struct sockaddr* addr,
  int* addrlen
);
int connect(
  SOCKET s,
  const struct sockaddr FAR* name,
  int namelen
);

Return Values

If no error occurs, accept returns a value of type SOCKET that is a descriptor for the new socket. This returned value is a handle for the socket on which the actual connection is made.

Otherwise, a value of INVALID_SOCKET is returned, and a specific error code can be retrieved by calling WSAGetLastError.

 

 

int recv(
  SOCKET s,
  char* buf,
  int len,
  int flags
);
int send(
  SOCKET s,
  const char FAR* buf,
  int len,
  int flags
);

int flags //The flag that specifies the way in which the call is made. (0 | MSG_OOB | MSG_PEEK)

 

 

unsigned long inet_addr(
  const char* cp
);
int  WSACleanup (void);

 

 

 

 

int bind(
  SOCKET s,
  const struct sockaddr FAR* name,
  int namelen
);

int listen(
  SOCKET s,
  int backlog
);
int backlog //Maximum length of the queue of pending connections

 

 

*******************************************************************

typedef u_int           SOCKET;

SOCKET socket(
  int af,
  int type,
  int protocol
);

int type, //SOCK_STREAM | SOCK_DGRAM

int protocol //IPPROTO_TCP | IPPROTO_UDP
注：所谓的套接字类型(SOCKET)、协议类型(type)、句柄(HANDLE)，以及套接字种类(Type)其本身都只是int 整型或者u_int，是一个32位的数字. 你给函数参数指定一个数值，系统就自动调用对应的各种类型数据(然而，实际上，内部全部是封装的，它的实现机制你一窍不通!)