Winsock网络编程笔记（2）----基于TCP的server和client

今天抽空看了一些简单的东西，主要是对服务器server和客户端client的简单实现。

面向连接的server和client，其工作流程如下图所示：

服务器和客户端将按照这个流程就行开发。。（个人觉得：通过这个流程图，Server应该要先于Client启动，不然Client的connect函数的执行就会出错啦，不知道我的个人感觉对不对，后面试试就知道了。。O(∩_∩)O~）

注意：上图的Server和Client的工作流程是基于面向有连接通信的工作流程，如果是无连接的通信，则不必调用listen和accept。在无连接的通信中，Server调用recvfrom函数来接收消息

在编写服务器和客户端之前，需要对TCP状态有所了解。。在server和client通信之间，二者都是通过发送/接收不同的信号来改变自己的状态，其tcp状态转换图如下：

Winsock网络编程笔记（2）----基于TCP的server和client

了解了二者的开发流程，就可以通过接口来具体实现。

简单的server代码实现：

 1 #include"winsock2.h"
 2 #include<iostream>
 3 using namespace std;
 4 //This line is very important
 5 
 6 #pragma comment(lib,"ws2_32.lib")
 7 int main()
 8 {
 9     WSADATA              wsaData;
10     SOCKET               ListeningSocket;
11     SOCKET               NewConnection;
12     SOCKADDR_IN          ServerAddr;
13     SOCKADDR_IN          ClientAddr;
14     int                  ClientAddrLen;
15     int                  Port = 5150;
16     int                  Ret;
17     char                 DataBuffer[1024];
18 
19     if ((Ret = WSAStartup(MAKEWORD(2,2), &wsaData)) != 0)
20     {
21         cout<<"WSAStartup failed with error "<<Ret<<endl;
22         //here no WSACleanup，because we do not create anything;
23         return -1;
24     }
25 
26     // Create a new socket to listening for client connections.
27     ListeningSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
28     if ( INVALID_SOCKET == ListeningSocket)
29     {
30         cout<<"Socket failed with error "<<WSAGetLastError()<<endl;
31         WSACleanup();
32         return -1;
33     }
34 
35     ServerAddr.sin_family = AF_INET;
36     ServerAddr.sin_addr.s_addr = htonl(INADDR_ANY);
37     ServerAddr.sin_port = htons(Port);
38 
39     //to bind
40     if (bind(ListeningSocket, (SOCKADDR *)&ServerAddr, sizeof(ServerAddr)) == SOCKET_ERROR)
41     {
42         cout<<"Binding failed with error "<<WSAGetLastError()<<endl;
43         closesocket(ListeningSocket);
44         WSACleanup();
45         return -1;
46     }
47 
48     // Listen for client connections. We used a backlog of 5 which is
49     // normal for many applications.
50 
51     if (listen(ListeningSocket,5) == SOCKET_ERROR)
52     {
53         cout<<"Listen failed with error "<<WSAGetLastError()<<endl;
54         closesocket(ListeningSocket);
55         WSACleanup();
56         return -1;
57     }
58 
59     cout<<"** We are waiting for a connection on port "<<Port<<"**"<<endl;
60 
61     //accep a connection when one arrives
62 
63     NewConnection = accept(ListeningSocket,(SOCKADDR*)&ClientAddr,&ClientAddrLen);
64     if (INVALID_SOCKET == NewConnection)
65     {
66         cout<<"Accept failed with error "<<WSAGetLastError()<<endl;
67         closesocket(ListeningSocket);
68         WSACleanup();
69         return -1;
70     }
71 
72     cout<<"** We successfully got a connection from "<<inet_ntoa(ClientAddr.sin_addr)
73         <<":port "<<ntohs(ClientAddr.sin_port)<<"!!**"<<endl;
74 
75     closesocket(ListeningSocket);
76     cout<<"** We are waiting for data...**\n";
77 
78     Ret = recv(NewConnection,DataBuffer,sizeof(DataBuffer),0);
79     if (SOCKET_ERROR == Ret)
80     {
81         cout<<"Recv failed with error "<<WSAGetLastError()<<endl;
82         closesocket(NewConnection);
83         WSACleanup();
84         return -1;
85     }
86 
87     cout<<"**We have successfully recieve "<<Ret<<" Byte(s) data!**\n";
88 
89     cout<<"**We are going to close the client connection...**\n";
90 
91     closesocket(NewConnection);
92     WSACleanup();
93 
94     return 0;
95 }

Server Code