udp 网络应用程序
Ws2_32.lib
#include <WinSock2.h>
#include <stdio.h>
void main()
{
WORD wVersionRequested;
WSADATA wsaData;
int err;
wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup( wVersionRequested, &wsaData );
if ( err != 0 ) {
/* Tell the user that we could not find a usable */
/* WinSock DLL. */
return;
}
/* Confirm that the WinSock DLL supports 2.2.*/
/* Note that if the DLL supports versions greater */
/* than 2.2 in addition to 2.2, it will still return */
/* 2.2 in wVersion since that is the version we */
/* requested. */
if ( LOBYTE( wsaData.wVersion ) != 1 ||
HIBYTE( wsaData.wVersion ) != 1 ) {
/* Tell the user that we could not find a usable */
/* WinSock DLL. */
WSACleanup( );
return;
}
/* The WinSock DLL is acceptable. Proceed. */
SOCKET sockSrv = socket(AF_INET,SOCK_DGRAM, 0 ); SOCKADDR_IN addrSrv ; addrSrv.sin_addr.S_un.S_addr = htonl(INADDR_ANY); addrSrv.sin_family = AF_INET; addrSrv.sin_port = htons(6000); bind(sockSrv,(SOCKADDR*)&addrSrv,sizeof(SOCKADDR));
SOCKADDR_IN addrClient; int len = sizeof(SOCKADDR);
char recvBuf[100];
recvfrom(sockSrv, recvBuf,100,0,(SOCKADDR*)&addrClient,&len);
printf("%s/n",recvfrom);
closesocket(sockSrv);
WSACleanup();
}
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WSAStartup （） 用于加载套接字 1 加载套接字库 2 进行套接字库的版本协商
socket
The socket function creates a socket that is bound to a specific service provider.
SOCKET socket( int af, int type, int protocol ）； 创建套接字， 第一个参数 指点地址组，AF——INET（TCPIP） 第二是 socket 的类型 （socket——stream or socket——dgram）第三个是 与特定的地址家族相关的协议Return ValuesIf no error occurs, socket returns a descriptor referencing the new socket. Otherwise, a value of INVALID_SOCKET is returned, and a specific error code can be retrieved by calling WSAGetLastError.
-----------------------------
The bind function associates a local address with a socket.
int bind( SOCKET s, 要指定的绑定的 socket const struct sockaddr FAR *name, 指定 套接字的本地地址信息 int namelen 本地地址信息 的大小);inet_addr
The inet_addr function converts a string containing an (Ipv4) Internet Protocol dotted address into a proper address for the IN_ADDR structure.
unsigned long inet_addr( const char FAR *cp 指定一个以点分十进制根式表示的ip地址 ); 返回一个适合分配给s_addr 的u ——long 类型的数值Parameters
- cp
- [in] Null-terminated character string representing a number expressed in the Internet standard ".'' (dotted) notation.
The listen function places a socket a state where it is listening for an incoming connection.
int listen( SOCKET s, 套接字描述符 int backlog 等待连接队列的最大长度 );accept
The accept function permits an incoming connection attempt on a socket.
SOCKET accept( SOCKET s, 套接字已经通过listen 函数将其设为监听状态 struct sockaddr FAR *addr,指向一个缓冲区的指针 该缓冲区用来接收实体地址也就是当客户想服务器发起连接的时候 服务器接收这个连接，保存发起连接的这个客户端的IP 地址信息的端口信息int FAR *addrlen );The send function sends data on a connected socket.int send( SOCKET s, const char FAR *buf, int len, int flags );Parameters
- s
- [in] Descriptor identifying a connected socket.
- buf
- [in] Buffer containing the data to be transmitted.
- len
- [in] Length of the data in buf.
- flags
- [in] Indicator specifying the way in which the call is made.
-
recv
The recv function receives data from a connected or bound socket.
int recv( SOCKET s, char FAR *buf, int len, int flags );
Parameters
- s
- [in] Descriptor identifying a connected socket.
- buf
- [out] Buffer for the incoming data.
- len
- [in] Length of buf.
- flags
- [in] Flag specifying the way in which the call is made.
-
connect
The connect function establishes a connection to a specified socket.
int connect( SOCKET s, 即将在其上建立连接的那个套接字 const struct sockaddr FAR *name, 设定连接的服务器端的地址信息 int namelen );
Parameters
- s
- [in] Descriptor identifying an unconnected socket.
- name
- [in] Name of the socket to which the connection should be established.
- namelen
- [in] Length of name.
recvfrom
The recvfrom function receives a datagram 数据报and stores 保存 the source address.
int recvfrom( SOCKET s, char FAR* buf, int len, int flags, struct sockaddr FAR *from, int FAR *fromlen );
sendto
The sendto function sends data to a specific destination.
int sendto( SOCKET s, const char FAR *buf, int len, int flags, const struct sockaddr FAR *to, int tolen );htons 把一个ushort （16）类型的值 从主机字节顺序转换为tcpip 的网络字节序htonl -----ulong （32）-----------
#include <Winsock2.h>
#include <stdio.h>
void main()
{
WORD wVersionRequested;
WSADATA wsaData;
int err;
wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup( wVersionRequested, &wsaData );
if ( err != 0 ) {
/* Tell the user that we could not find a usable */
/* WinSock DLL. */
return;
}
/* Confirm that the WinSock DLL supports 2.2.*/
/* Note that if the DLL supports versions greater */
/* than 2.2 in addition to 2.2, it will still return */
/* 2.2 in wVersion since that is the version we */
/* requested. */
if ( LOBYTE( wsaData.wVersion ) != 1 ||
HIBYTE( wsaData.wVersion ) != 1 ) {
/* Tell the user that we could not find a usable */
/* WinSock DLL. */
WSACleanup( );
return;
}
/* The WinSock DLL is acceptable. Proceed. */
SOCKET sockClient= socket(AF_INET,SOCK_DGRAM, 0 );
SOCKADDR_IN addrSrv ;
addrSrv.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
addrSrv.sin_family = AF_INET; addrSrv.sin_port = htons(6000);
sendto(sockClient,"hello",strlen("hello")+1,0,(SOCKADDR*)&addrSrv,sizeof(SOCKADDR));
closesocket(sockClient);
WSACleanup();
}