I'am having some trouble to make a Duplex communication between a C# server and a C++ work:
The objective is to create the pipe, read something from the client and write something back.
Everything is working fine if i'm just reading from the client or just writing to the client but I can't do both one after the other!
Here's my C# server:
// Create a name pipe
using (NamedPipeServerStream pipeStream = new NamedPipeServerStream("TestPipe"))
{
Console.WriteLine("[Server] Pipe created {0}", pipeStream.GetHashCode());
// Wait for a connection
pipeStream.WaitForConnection();
Console.WriteLine("[Server] Pipe connection established");
//Reading Part
using (StreamReader sr = new StreamReader(pipeStream))
{
string temp;
while ((temp = sr.ReadLine()) != null)
{
Console.WriteLine("{0}: {1}", DateTime.Now, temp);
}
}
//Writing Part
using (StreamWriter sw = new StreamWriter(pipeStream))
{
sw.AutoFlush = true;
String st = "send Back\0";
sw.WriteLine(st);
}
}
And Here is the C++ client:
HANDLE hFile;
BOOL flg;
DWORD dwWrite;
char szPipeUpdate[200];
hFile = CreateFile(L"\\\\.\\pipe\\TestPipe", GENERIC_WRITE|GENERIC_READ,
0, NULL, OPEN_EXISTING,
0, NULL);
strcpy(szPipeUpdate,"Sending some data from client to server!");
if(hFile == INVALID_HANDLE_VALUE)
{
DWORD dw = GetLastError();
printf("CreateFile failed for Named Pipe client\n:" );
}
else
{
flg = WriteFile(hFile, szPipeUpdate, strlen(szPipeUpdate), &dwWrite, NULL);
if (FALSE == flg)
{
printf("WriteFile failed for Named Pipe client\n");
}
else
{
printf("WriteFile succeeded for Named Pipe client\n");
}
}
printf("Let's read!\n");
//Read the datas sent by the server
BOOL fFinishRead = FALSE;
do
{
char chResponse[200];
DWORD cbResponse, cbRead;
cbResponse = sizeof(chResponse);
fFinishRead = ReadFile(
hFile, // Handle of the pipe
chResponse, // Buffer to receive the reply
cbResponse, // Size of buffer in bytes
&cbRead, // Number of bytes read
NULL // Not overlapped
);
if (!fFinishRead && ERROR_MORE_DATA != GetLastError())
{
DWORD dwError = GetLastError();
wprintf(L"ReadFile from pipe failed w/err 0x%08lx\n", dwError);
break;
}
std::cout << chResponse;
} while (!fFinishRead); // Repeat loop if ERROR_MORE_DATA
CloseHandle(hFile);
With the Server & Client NamedPipeStreams you need to make sure at least one end of the connection is attempting to read at all times, otherwise writes will fail. I'd guess it's a timing issue between your client & server around whichever is listening/writing. Here's a quick blog post explaining this behavior as well.
I'd recomend using two streams on the client & server, both reading/writing from the same pipe.
Related
I'm trying to write a C# console app to interface with a PC Miler telnet server. I managed to get this to work in powershell, but my C# code is not working.
static void Main(string[] args)
{
byte[] ReadBuffer = new byte[1024];
string[] stringSeparators = new string[]{"READY"};
try
{
TcpClient Socket = new TcpClient("myServer", 8320);
if (Socket.Connected) {
NetworkStream netStream = Socket.GetStream();
string PCMSResponse = "";
// Check for the READY prompt
if (netStream.CanRead) {
int byteRead = 0;
while (netStream.DataAvailable) {
byteRead = netStream.Read(ReadBuffer, 0, ReadBuffer.Length);
PCMSResponse += Encoding.ASCII.GetString(ReadBuffer, 0 , byteRead).Trim();
}
} else {
Console.WriteLine("Cannot read from myServer");
}
Thread.Sleep(1000);
// Get New Trip
if (netStream.CanWrite) {
Byte[] PCMSCommandBuffer = Encoding.ASCII.GetBytes("PCMSNewTrip");
netStream.Write(PCMSCommandBuffer, 0 , PCMSCommandBuffer.Length);
Thread.Sleep(1000);
} else {
Console.WriteLine("Cannot write to myServer.");
}
if (netStream.CanRead) {
int byteRead = 0;
while (netStream.DataAvailable) {
byteRead = netStream.Read(ReadBuffer, 0, ReadBuffer.Length);
PCMSResponse += Encoding.ASCII.GetString(ReadBuffer, 0, byteRead).Trim();
}
} else {
Console.WriteLine("Cannot read from myServer");
}
string[] ResponseArray = PCMSResponse.Split(stringSeparators, StringSplitOptions.None);
int c = ResponseArray.Length - 2;
string TripID = ResponseArray[c].Replace(System.Environment.NewLine, "").Replace("\0", "");
Console.WriteLine(PCMSResponse);
}
}
catch (SocketException)
{
Console.WriteLine("Unable to connect to server")
}
}
Expected output
ALK PCMILER SERVER READY
pcmsnewtrip
53
READY
Actual output
ALK PCMILER SERVER READY
It seems like I am not actually writing to the server because if I were to write an invalid command to the server I would see an error like this:
ALK PCMILER SERVER READY
pmctripnew
NO SUCH FUNCTION
READY
I know I can write to the socket because I'm not getting my error message Cannot write to myServer.
Not sure what I'm doing wrong. :(
Let me know if you'd also like to see the powershell code.
EDIT - If you're going to edit this post, at least keep the expected output AS EXPECTED! Changing the expected output changes the intent of the post. (EG, if I want apples but you edit my post to ask for oranges, I'm not going to get the correct answer.)
So the issue turns out to be that the NetworkStream.Write method does not end a string with a line terminator. As a result, when I wrote my PCMSCommandBuffer bytes to the stream, the command was never processed by the server (because its waiting for more of the command or the enter key to let it know you're done). My solution was to assign the stream to a StreamWriter. Then I can use the WriteLine method whichdoes send a line terminator.
streamWriter = new StreamWriter(netStream);
// Get New Trip
if (netStream.CanWrite) {
Byte[] PCMSCommandBuffer = Encoding.ASCII.GetBytes("PCMSNewTrip");
//netStream.Write(PCMSCommandBuffer, 0 , PCMSCommandBuffer.Length);
streamWriter.WriteLine("PCMSNewTrip");
//netStream.Flush();
streamWriter.Flush();
Console.WriteLine(PCMSCommandBuffer.Length + " PCMSNewTrip");
Thread.Sleep(1000);
} else {
Console.WriteLine("Cannot write to EW-APP1.");
}
I have learned about Named Pipe and try to send the message from C++ and C# application and it works fine. But I am not able to send the image from C++ side to C# using Named Pipe. Can anyone please tell me how I can do this.
My C# Code for Named Pipe
static void Main(string[] args)
{
Console.WriteLine("Creating Client Pipe");
NamedPipeClientStream pipe = new NamedPipeClientStream(".", "HyperPipe", PipeDirection.InOut);
Console.WriteLine("Pipe Created Successfully, Connecting to Server");
pipe.Connect();
Console.WriteLine("Successfully, Connected to Server");
using (StreamReader rdr = new StreamReader(pipe, Encoding.Unicode))
{
System.Console.WriteLine("Message from Server: " + rdr.ReadToEnd());
}
Console.ReadKey();
}
and C++ Code
int _tmain(int argc, _TCHAR* argv[])
{
cout << "Server Creating Pipe\n";
HANDLE hPipe = ::CreateNamedPipe(_T("\\\\.\\pipe\\HyperPipe"),
PIPE_ACCESS_DUPLEX,
PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE,
PIPE_UNLIMITED_INSTANCES,
4096,
4096,
0,
NULL);
cout << "Server Created Succesfully";
ConnectNamedPipe(hPipe, NULL);
LPTSTR data = _T("Hello");
cout << "Sending Message to Client";
DWORD bytesWritten = 0;
WriteFile(hPipe, data, _tcslen(data) * sizeof(TCHAR), &bytesWritten, NULL);
CloseHandle(hPipe);
return 0;
}
What I want is when the I enter the path on the C# side it will send that to C++ and using OpenCV library I will fetch that image from the memory and send to the C#.
Thanks in Advance
Have you tried converting your image to an array of bytes, and then sending it the same way you did with the text ?
In my client/server application my client wiil communicate with the server for 2 functions: the client will either request data from the server or it will send data so the server will save it. I'm using one socket for both methods, and the method to be used is defined by the first byte sent. If the first byte is "1" it is requesting data. If it is "2", it will send data (data bytes are sent after the "2" byte). It works perfectly for sending data. But when I'm requesting data it works, as long as I don't read the socket stream in the client. It's like if I make the client read data after sending data, the server will have no data to read, and it just crashes when trying to read the data.
Here is my server code:
private const int BufferSize = 1024;
NetworkStream netstream = null;
byte[] RecData = new byte[BufferSize];
int RecBytes;
try {
netstream = clientSocket.GetStream();
int totalrecbytes = 0;
using (MemoryStream ms = new MemoryStream()) {
//When I get here, there is no data to read
while ((RecBytes = netstream.Read(RecData, 0, RecData.Length)) > 0) {
ms.Write(RecData, 0, RecBytes);
totalrecbytes += RecBytes;
}
byte[] bytes = ms.ToArray();
byte b = bytes[0];
switch (b) {
case 1:
//Here I gather data and put it in "stream" variable
byte[] SendingBuffer = null;
int NoOfPackets = Convert.ToInt32(Math.Ceiling(Convert.ToDouble(stream.Length) / Convert.ToDouble(BufferSize)));
int TotalLength = (int)stream.Length, CurrentPacketLength, counter = 0;
for (int i = 0; i < NoOfPackets; i++) {
if (TotalLength > BufferSize) {
CurrentPacketLength = BufferSize;
TotalLength = TotalLength - CurrentPacketLength;
}
else
CurrentPacketLength = TotalLength;
SendingBuffer = new byte[CurrentPacketLength];
stream.Read(SendingBuffer, 0, CurrentPacketLength);
netstream.Write(SendingBuffer, 0, (int)SendingBuffer.Length);
}
netstream.Flush();
}
catch (Exception e) {
Console.WriteLine("EXCEPTION:\n" + e.ToString());
}
break;
case 2:
//Code to read data
break;
}
}
netstream.Close()
clientSocket.Close();
And here is my client code:
using (System.Net.Sockets.TcpClient clientSocket = new System.Net.Sockets.TcpClient()) {
string returnData = "";
IAsyncResult ar = clientSocket.BeginConnect("127.0.0.1", 8080, null, null);
System.Threading.WaitHandle wh = ar.AsyncWaitHandle;
try {
if (!ar.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(5), false)) {
clientSocket.Close();
Console.WriteLine("Timeout");
return;
}
System.Net.Sockets.NetworkStream serverStream = clientSocket.GetStream();
byte b = 1;
byte[] outStream = { b };
serverStream.Write(outStream, 0, outStream.Length);
serverStream.Flush();
//If I comment following lines, the server can read sent data, but server can't otherwise
byte[] RecData = new byte[1024];
int RecBytes;
int totalrecbytes = 0;
MemoryStream MS = new MemoryStream();
while ((RecBytes = serverStream.Read(RecData, 0, RecData.Length)) > 0) {
MS.Write(RecData, 0, RecBytes);
totalrecbytes += RecBytes;
}
serverStream.Close();
clientSocket.Close();
clientSocket.EndConnect(ar);
}
catch (Exception ex) {
Console.WriteLine("Exceção: " + ex.ToString());
}
finally {
wh.Close();
}
}
So, how can I send data to server and read the response? (I tried even putting the thread to sleep after sending data, with no luck.)
Thanks in advance.
EDIT:
With some debug messages I discovered that the server do read the "1" byte that was sent, but somehow it gets stuck inside the while loop, like, the server just stops there, no more loops and it does not leave the while loop. I saw that after writing "loop" in console inside the while loop, and writing read bytes also in console. It wrote "loop" once, and the read byte.
This code worries me:
//When I get here, there is no data to read
while ((RecBytes = netstream.Read(RecData, 0, RecData.Length)) > 0) {
ms.Write(RecData, 0, RecBytes);
totalrecbytes += RecBytes;
}
You are reading until the client closes the connection (or shuts down sending, which you don't do). But the client only closes when the server has replied. The server reply will never come. It is a deadlock.
Solution: Read a single byte to determine the requests command (b).
Unrelated to the question, your "packetised" sending (NoOfPackets, ...) does not seem to serve any purpose. Just use Stream.Copy to write. TCP does not have packets.
An even better solution would be to abandon your custom TCP protocol and use an HTTP library. All these concerns just go away. There are various smaller problems with your code that are very typical to see in TCP code.
I'm fairly new to socket programming, but, using an online tutorial, I've successfully sent a short string from one machine to another using C.
The problem I'm having is with trying to send a string from a client written in C#. The server (written in C) prints out a blank/empty string.
Here is the C code that runs on the "server" machine (in this case a router running OpenWRT):
int main(int argc, char *argv[])
{
int listenfd = 0, connfd = 0;
struct sockaddr_in serv_addr;
char recvBuff[1025];
int bytesRead;
listenfd = socket(AF_INET, SOCK_STREAM, 0);
memset(&serv_addr, '0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(1234);
bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
printf("Listening for string on port 1234...\n");
listen(listenfd, 10);
while(1)
{
connfd = accept(listenfd, (struct sockaddr*)NULL, NULL);
bytesRead = recv(connfd, recvBuff, 1024, 0); // Receive string
if (bytesRead < 0)
{
printf("Error reading from stream\n");
}
recvBuff[bytesRead] = 0; // null-terminate the string
printf("%d:%s\n", bytesRead, recvBuff);
close(connfd);
sleep(1);
}
}
When sending this little server a string from another C program it works exactly as expected (prints the string out then waits for another one). [Note: I don't think the C client's code is relevant, but I can post it if need be]
However, when trying to send it a string from a C# program (copied below), the server prints out 0: (i.e. 0 bytes read, followed by an empty string) and I can't for the life of me figure out what the issue is. Both apps are pretty straightforward, so I'm assuming I should be using something other than WriteLine (I've also tried Write but to no avail).
C# Client:
namespace SocketTest
{
class Program
{
static void Main(string[] args)
{
TcpClient client = new TcpClient("10.45.13.220", 1234);
Stream stream = client.GetStream();
StreamWriter writer = new StreamWriter(stream);
writer.WriteLine("Testing...");
client.Close();
}
}
}
To null terminate a string use
recvBuff[bytesRead] = '\0';
And call close on writer (which causes the writer to flush any pending bytes)
writer.WriteLine("Testing...");
writer.Close();
client.Close();
I am trying to have a 2-way communication between a VC++ 6 app and a C# app. I am using named pipes. In my C++ code I can read the message from the C# client but then the server "dies" and I have to restart it again.
What I want to do is have the C# app connect to the C++ app, request a status, and the C++ app goes off and checks the status, and then returns either "busy" or "idle".
I can't write anything back to the C# client as it says the connection has been closed. Some things I have commented out are things I have tried already.
C++ code (started as a thread)
UINT CNamedPipe::StartNamedPipeServer()
{
LPTSTR lpszPipename = "\\\\.\\pipe\\SAPipe";
HANDLE hPipe;
BOOL flg;
DWORD dwWrite,dwRead;
char szServerUpdate[200];
char szClientUpdate[200];
hPipe = CreateNamedPipe ( lpszPipename,
PIPE_ACCESS_DUPLEX,
PIPE_TYPE_MESSAGE |
PIPE_READMODE_MESSAGE |
PIPE_NOWAIT, //changed from nowait
PIPE_UNLIMITED_INSTANCES, // max. instances
BUFSIZE, // output buffer size
BUFSIZE, // input buffer size
PIPE_TIMEOUT, // client time-out
NULL); // no security attribute
if (hPipe == INVALID_HANDLE_VALUE)
return 0;
ConnectNamedPipe(hPipe, NULL);
while(m_bServerActive) //This seems to work well ....
{
//Read from client
flg = ReadFile(hPipe,szClientUpdate,strlen(szClientUpdate),&dwRead, NULL);
if(flg) //Read something from the client!!!!
{
CString csMsg,csTmp;
for(int i=0;i<dwRead;i++){
csTmp.Format("%c",szClientUpdate[i]);
csMsg += csTmp;
}
AfxMessageBox("Client message: " + csMsg);
strcpy( szServerUpdate,"busy");
//Write status to Client
flg = WriteFile(hPipe, szServerUpdate, strlen(szServerUpdate), &dwWrite, NULL);
EndServer();
StartServer();
}
}
return 0;
}
C# Code:
public void ThreadStartClient(object obj)
{
// Ensure that we only start the client after the server has created the pipe
ManualResetEvent SyncClientServer = (ManualResetEvent)obj;
// Only continue after the server was created -- otherwise we just fail badly
// SyncClientServer.WaitOne();
using (NamedPipeClientStream pipeStream = new NamedPipeClientStream(".", "SAPipe"))
{
// The connect function will indefinately wait for the pipe to become available
// If that is not acceptable specify a maximum waiting time (in ms)
pipeStream.Connect();
//Write from client to server
using (StreamWriter sw = new StreamWriter(pipeStream))
{
sw.WriteLine("What's your status?");
}
//Read server reply
/*using (StreamReader sr = new StreamReader(pipeStream))
{
string temp = "";
temp = sr.ReadLine(); //Pipe is already closed here ... why?
MessageBox.Show(temp);
}*/
//pipeStream.Close();
}
}
}
Disposing of a StreamWriter or StreamReader will close the underlying stream.
Your using statements therefore will be causing the stream to close.
public void ThreadStartClient(object obj)
{
// Ensure that we only start the client after the server has created the pipe
ManualResetEvent SyncClientServer = (ManualResetEvent)obj;
// Only continue after the server was created -- otherwise we just fail badly
// SyncClientServer.WaitOne();
using (NamedPipeClientStream pipeStream = new NamedPipeClientStream(".", "SAPipe"))
{
// The connect function will indefinately wait for the pipe to become available
// If that is not acceptable specify a maximum waiting time (in ms)
pipeStream.Connect();
//Write from client to server
StreamWriter sw = new StreamWriter(pipeStream))
sw.WriteLine("What's your status?");
//Read server reply
StreamReader sr = new StreamReader(pipeStream)
string temp = "";
temp = sr.ReadLine(); //Pipe is already closed here ... why?
MessageBox.Show(temp);
}
}
It should also be noted that because you wrap your stream in a using statement, the commented out pipeStream.Close() function isn't needed.
Ok, got it working for my application .... thanks Blam !
Here's the C++ server (run this inside a thread):
UINT CNamedPipe::StartNamedPipeServer()
{
if(!m_bServerActive)
return 0;
LPTSTR lpszPipename = "\\\\.\\pipe\\MyPipe";
HANDLE hPipe;
BOOL flg;
DWORD dwWrite,dwRead;
char szServerUpdate[200];
char szClientUpdate[200];
hPipe = CreateNamedPipe ( lpszPipename,
PIPE_ACCESS_DUPLEX,
PIPE_TYPE_MESSAGE |
PIPE_READMODE_MESSAGE |
PIPE_WAIT, //HAS TO BE THIS
PIPE_UNLIMITED_INSTANCES, // max. instances
BUFSIZE, // output buffer size
BUFSIZE, // input buffer size
PIPE_TIMEOUT, // client time-out
NULL); // no security attribute
if (hPipe == INVALID_HANDLE_VALUE)
return 0;
ConnectNamedPipe(hPipe, NULL);
strcpy( szServerUpdate,"busy");
//Write status to Client
flg = WriteFile(hPipe, szServerUpdate, strlen(szServerUpdate), &dwWrite, NULL);
EndServer();
StartServer();
return 0;
}
And here's the C# client:
public void ThreadStartClient(object obj)
{
// Ensure that we only start the client after the server has created the pipe
ManualResetEvent SyncClientServer = (ManualResetEvent)obj;
using (NamedPipeClientStream pipeStream = new NamedPipeClientStream(".", "MyPipe", PipeDirection.InOut))
{
// The connect function will indefinately wait for the pipe to become available
// If that is not acceptable specify a maximum waiting time (in ms)
pipeStream.Connect();
if (!pipeStream.IsConnected) //It thinks it's connected but can't read anything ....
{
MessageBox.Show("Failed to connect ....");
return;
}
//Read server reply
StreamReader sr = new StreamReader(pipeStream);
char[] c = new char[200];
while (sr.Peek() >= 0)
{
sr.Read(c, 0, c.Length);
}
string s = new string(c);
MessageBox.Show(s);
}
}
I'm not actually sending anything from the client to the server because I don't need to ... the key thing in this was the PIPE_WAIT parameter in the CreateNamedPipe() function. This makes the server wait for a client connection.