下面是数据传输的重点-CDataSocket类，函数不多，都比较重要。
1、OnAccept 数据tcp服务器被连接的虚函数，由框架调用。
1 void CDataSocket::OnAccept(int nErrorCode)
2 {
3 // Accept the connection using a temp CSocket object.
4 CAsyncSocket tmpSocket;
5 Accept(tmpSocket);
6
7 SOCKET socket = tmpSocket.Detach();
8 Close();
9
10 Attach(socket);
11
12 m_bConnected = TRUE;
13
14 CAsyncSocket::OnAccept(nErrorCode);
15 }
第7行 得到套接字描述符socket。第8行关闭监听的这个套接字，第11行关联socket与本对象，第12行，标记连接标志。这种处理方法少写一个类。因为tcp监听得一个socket，而连接上来的客户端也需要一个socket来与之通信。这样做适合只有一个客户端的情况。
2、OnReceive 数据接收处理函数
1 int CDataSocket::Receive()
2 {
3 TRACE("OnReceive\n");
4 int nRead = 0;
5
6 if (m_pControlSocket->m_nStatus == STATUS_UPLOAD)
7 {
8 if (m_File.m_hFile == NULL)
9 return 0;
10
11 byte data[PACKET_SIZE];
12 nRead = CAsyncSocket::Receive(data, PACKET_SIZE);
13
14 switch(nRead)
15 {
16 case 0:
17 {
18 m_File.Close();
19 m_File.m_hFile = NULL;
20 Close();
21 // tell the client the transfer is complete.
22 m_pControlSocket->SendResponse("226 Transfer complete");
23 // destroy this socket
24 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
25 break;
26 }
27 case SOCKET_ERROR:
28 {
29 if (GetLastError() != WSAEWOULDBLOCK)
30 {
31 m_File.Close();
32 m_File.m_hFile = NULL;
33 Close();
34 m_pControlSocket->SendResponse("426 Connection closed; transfer aborted.");
35 // destroy this socket
36 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
37 }
38 break;
39 }
40 default:
41 {
42 TRY
43 {
44 m_File.Write(data, nRead);
45 }
46 CATCH_ALL(e)
47 {
48 m_File.Close();
49 m_File.m_hFile = NULL;
50 Close();
51 m_pControlSocket->SendResponse("450 Can‘t access file.");
52 // destroy this socket
53 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
54 return 0;
55 }
56 END_CATCH_ALL;
57 break;
58 }
59 }
60 }
61 return nRead;
62 }
如果处于上传状态，那么将接收到的数据写入文件。
3、PreSendFile 与发送文件有关的函数
1 BOOL CDataSocket::PrepareSendFile(LPCTSTR lpszFilename)
2 {
3 // close file if it‘s already open
4 if (m_File.m_hFile != NULL)
5 {
6 m_File.Close();
7 }
8
9 // open source file
10 if (!m_File.Open(lpszFilename, CFile::modeRead | CFile::typeBinary))
11 {
12 return FALSE;
13 }
14 m_nTotalBytesSend = m_File.GetLength();
15
16 if (m_pControlSocket->m_dwRestartOffset < m_nTotalBytesSend)
17 {
18 m_nTotalBytesTransfered = m_pControlSocket->m_dwRestartOffset;
19 }
20 else
21 {
22 m_nTotalBytesTransfered = 0;
23 }
24 return TRUE;
25 }
初始化文件描述符m_File，m_nTotalBytesSend,m_nTotalBytesTransfered。
4、 SendFile函数 调用PrepareSendFile，调用OnSend发送文件。
1 void CDataSocket::SendFile(LPCTSTR lpszFilename)
2 {
3 if (!PrepareSendFile(lpszFilename))
4 {
5 // change status
6 m_pControlSocket->m_nStatus = STATUS_IDLE;
7
8 m_pControlSocket->SendResponse("426 Connection closed; transfer aborted.");
9
10 // destroy this socket
11 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
12 return;
13 }
14 OnSend(0);
15 }
5、SendData 发送数据 是为了LIST命令而准备，发送文件目录列表。
6、OnSend 主要区分了list命令的情况和download的情况。
1 void CDataSocket::OnSend(int nErrorCode)
2 {
3 CAsyncSocket::OnSend(nErrorCode);
4 switch(m_pControlSocket->m_nStatus)
5 {
6 case STATUS_LIST:
7 {
8 while (m_nTotalBytesTransfered < m_nTotalBytesSend)
9 {
10 DWORD dwRead;
11 int dwBytes;
12
13 CString strDataBlock;
14
15 dwRead = m_strData.GetLength();
16
17 if (dwRead <= PACKET_SIZE)
18 {
19 strDataBlock = m_strData;
20 }
21 else
22 {
23 strDataBlock = m_strData.Left(PACKET_SIZE);
24 dwRead = strDataBlock.GetLength();
25 }
26
27 if ((dwBytes = Send(strDataBlock, dwRead)) == SOCKET_ERROR)
28 {
29 if (GetLastError() == WSAEWOULDBLOCK)
30 {
31 Sleep(0);
32 return;
33 }
34 else
35 {
36 TCHAR szError[256];
37 wsprintf(szError, "Server Socket failed to send: %d", GetLastError());
38
39 // close the data connection.
40 Close();
41
42 m_nTotalBytesSend = 0;
43 m_nTotalBytesTransfered = 0;
44
45 // change status
46 m_pControlSocket->m_nStatus = STATUS_IDLE;
47
48 m_pControlSocket->SendResponse("426 Connection closed; transfer aborted.");
49
50 // destroy this socket
51 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
52 }
53 }
54 else
55 {
56 m_nTotalBytesTransfered += dwBytes;
57 m_strData = m_strData.Mid(dwBytes);
58 }
59 }
60 if (m_nTotalBytesTransfered == m_nTotalBytesSend)
61 {
62 // close the data connection.
63 Close();
64
65 m_nTotalBytesSend = 0;
66 m_nTotalBytesTransfered = 0;
67
68 // change status
69 m_pControlSocket->m_nStatus = STATUS_IDLE;
70
71 // tell the client the transfer is complete.
72 m_pControlSocket->SendResponse("226 Transfer complete");
73 // destroy this socket
74 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
75 }
76 break;
77 }
78 case STATUS_DOWNLOAD:
79 {
80 while (m_nTotalBytesTransfered < m_nTotalBytesSend)
81 {
82 // allocate space to store data
83 byte data[PACKET_SIZE];
84
85 m_File.Seek(m_nTotalBytesTransfered, CFile::begin);
86
87 DWORD dwRead = m_File.Read(data, PACKET_SIZE);
88
89 int dwBytes;
90
91 if ((dwBytes = Send(data, dwRead)) == SOCKET_ERROR)
92 {
93 if (GetLastError() == WSAEWOULDBLOCK)
94 {
95 Sleep(0);
96 break;
97 }
98 else
99 {
100 TCHAR szError[256];
101 wsprintf(szError, "Server Socket failed to send: %d", GetLastError());
102
103 // close file.
104 m_File.Close();
105 m_File.m_hFile = NULL;
106
107 // close the data connection.
108 Close();
109
110 m_nTotalBytesSend = 0;
111 m_nTotalBytesTransfered = 0;
112
113 // change status
114 m_pControlSocket->m_nStatus = STATUS_IDLE;
115
116 m_pControlSocket->SendResponse("426 Connection closed; transfer aborted.");
117
118 // destroy this socket
119 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
120 }
121 }
122 else
123 {
124 m_nTotalBytesTransfered += dwBytes;
125 }
126 }
127 if (m_nTotalBytesTransfered == m_nTotalBytesSend)
128 {
129 // close file.
130 m_File.Close();
131 m_File.m_hFile = NULL;
132
133 // close the data connection.
134 Close();
135
136 m_nTotalBytesSend = 0;
137 m_nTotalBytesTransfered = 0;
138
139 // change status
140 m_pControlSocket->m_nStatus = STATUS_IDLE;
141
142 // tell the client the transfer is complete.
143 m_pControlSocket->SendResponse("226 Transfer complete");
144 // destroy this socket
145 AfxGetThread()->PostThreadMessage(WM_DESTROYDATACONNECTION, 0, 0);
146 }
147 break;
148 }
149 }
150 }
7、OnConnect函数 tcp连接成功时被框架调用的虚函数。
8、OnClose函数 当数据发送完成或者接收完成后被框架调用的虚函数。主要做清理工作。
9、
时间： 2024-10-14 04:45:34