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为了设计统一和用户操作方便，我们希望将服务端与客户端融合在一起，形成一个程序，这样用户理解起来，更加直观一点（其实这样做也是为了方便调试，大家可以在本机上测试，自己传文件给自己）。所以，我们在程序中需要使用两个winsock控件，一个负责监听，一个负责发送，当发送端连接成功以后，便选择一个待发送的文件（可以是任意二进制文件），接着将文件名和文件字节长度发送给接收端，接收端收到这个消息以后，将文件名和文件长度解析出来，然后通知发送端可以开始发送文件；发送端读到这个消息之后，将文件流以字节的形式发送到接收端，接收端收到后，将二进制流回写，保存成文件即可。这里要注意两点，一个是由于winsock每次最大传输8k的内容，所以需要将文件分解，每次传输固定数目的字节流，这样发送和接收时都可以根据这个数目来判断文件传输的进程，一旦字节流数目等于文件的大小，就需要关闭相应的文件句柄；另一点是由于我只使用一个winsock控件接收，接收文本时需要注意要将unicode转码，解析成可识别的信息。
源代码
下面的代码既是服务器又是客户端
采用应答式发送方式
自动拆分文件，包括2进制
option explicit
private declare sub sleep lib "kernel32" (byval dwmilliseconds as long)
dim mybyte() as byte 发送方数组
const filecomesmsg = "a file is coming " 有文件到来
const remoteisreadymsg = "sender is ready " 准备好了
const fileisovermsg = "the file is ended" 文件完毕
const remotedenymsg = "the user canceled" 用户取消
const filecountmsg = "the file lengh is" 文件长度
const recevieisreadymsg = "receiver is ready " 准备接收
dim arrdata() as byte 收到的信息
dim filesave as integer 保存文件的句柄
dim filehandle as integer 发送方文件的句柄
dim filesize as double 文件的大小
dim sendbyte as long
dim receivebyte as long
dim mylocation as double
dim mymsg as string 消息
dim fileisover as boolean 文件是否已经完毕
const receiveport = 7905
const buffer_size = 5734
private sub cmdconnect_click()
timer2.enabled = true
end sub
private sub cmdsend_click()
on error goto errorhandle
with commondialog1
.cancelerror = true
.dialogtitle = "选择您要传送的文件"
.filter = "all files (*.*)|*.*"
.showopen
end with
filehandle = freefile
open commondialog1.filename for binary access read as #filehandle
cmdsend.enabled = false
filesize = cdbl(filelen(commondialog1.filename))
label1.caption = "等待回应>>>"
msgbox ("选择的文件大小为 " & lof(filehandle) & " 字节")
if winsocksend.state = sckconnected then
winsocksend.senddata filecomesmsg & commondialog1.filename 发送发出文件信息
end if
exit sub
errorhandle:
cmdsend.enabled = true
msgbox ("你没有选择一个文件！")
end sub
private sub form_load()
winsockreceive.localport = receiveport
winsockreceive.listen
fileisover = true
label1.caption = "准备传输>>>"
end sub
public function sendchunk()
dim mybytesize as long
if winsocksend.state <> sckconnected then exit function
mybytesize = buffer_size
if lof(filehandle) – loc(filehandle) < buffer_size then mybytesize = (lof(filehandle) – loc(filehandle))
redim mybyte(0 to mybytesize – 1)
get #filehandle, , mybyte
winsocksend.senddata mybyte
sendbyte = sendbyte + mybytesize
progressbar1.value = int((100 / filesize) * sendbyte)
if sendbyte >= filesize then
fileisover = true
winsocksend.senddata fileisovermsg
end if
end function
private sub timer2_timer()
if winsocksend.state = sckconnected then
timer2.enabled = false
cmdconnect.enabled = false
elseif winsocksend.state <> 1 and winsocksend.state <> 6 and winsocksend.state <> 7 and winsocksend.state <> 8 and winsocksend.state <> 9 then
winsocksend.connect txthost.text, receiveport
elseif winsocksend.state = 8 or winsocksend.state = 9 then
winsocksend.close
end if
end sub
private sub winsockreceive_connectionrequest(byval requestid as long)
if winsockreceive.state <> sckclosed then winsockreceive.close
winsockreceive.accept requestid
end sub
private sub winsockreceive_dataarrival(byval bytestotal as long)
redim arrdata(0 to bytestotal – 1)
winsockreceive.getdata arrdata, vbbyte + vbarray
mymsg = strconv(arrdata, vbunicode) 二进制转为字符串
select case mid(mymsg, 1, 17)
case filecomesmsg 这些消息发送方和接受方都可收到
显示保存对话框
on error goto errorhandle
commondialog1.filename = mid(mymsg, 17, len(mymsg))
commondialog1.dialogtitle = "选择保存文件的路径"
commondialog1.showsave
filesave = freefile
receivebyte = 0
cmdsend.enabled = false
winsockreceive.senddata recevieisreadymsg
case fileisovermsg
close #filesave
msgbox ("文件传输成功！") 大家一起处理
cmdconnect.enabled = true
cmdsend.enabled = true
label1.caption = "准备传输>>>"
progressbar1.value = 0
winsockreceive.senddata fileisovermsg
winsockreceive.close
winsockreceive.listen
case filecountmsg
filesize = mid(mymsg, 18, len(mymsg))
open commondialog1.filename for binary access write as #filesave
winsockreceive.senddata remoteisreadymsg
label1.caption = "文件准备传输！"
fileisover = false
case else
if receivebyte < filesize then
receivebyte = receivebyte + bytestotal
put #filesave, , arrdata
winsockreceive.senddata remoteisreadymsg
progressbar1.value = int((100 / filesize) * receivebyte)
end if
end select
exit sub
errorhandle:
winsockreceive.senddata remotedenymsg
cmdconnect.enabled = true
end sub
private sub winsocksend_dataarrival(byval bytestotal as long)
winsocksend.getdata mymsg
select case mymsg
case recevieisreadymsg
winsocksend.senddata filecountmsg & filesize
fileisover = false
sendbyte = 0
case remoteisreadymsg
如果文件还没有结束，继续传输
if not fileisover then
label1.caption = "文件正在被传输>>>"
sendchunk
else
winsocksend.senddata fileisovermsg
end if
case fileisovermsg
主机处理
close #filehandle
msgbox ("文件传输成功！") 大家一起处理
winsocksend.senddata fileisovermsg
winsocksend.close
cmdconnect.enabled = true
progressbar1.value = 0
cmdsend.enabled = true
label1.caption = "准备传输>>>"
case remotedenymsg
msgbox ("用户终止了传输！")
cmdsend.enabled = true
label1.caption = "准备传输>>>"
close #filehandle
end select
exit sub
end sub
