Ehsan Akbar Ehsan Akbar - 2 months ago 19
C++ Question

Send data to a tcp/port in c++ visual studio

I create two applications server and client in c# and they work.I need to change the client application to c++ .Here is my code in c# :

m_clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPAddress ip = IPAddress.Parse("127.0.0.1");
int iPortNo = System.Convert.ToInt16("5000");
IPEndPoint ipEnd = new IPEndPoint(ip, iPortNo);
m_clientSocket.Connect(ipEnd);
if (m_clientSocket.Connected)
{
byte[] packet = CreateMessage("salam");
if (m_clientSocket != null)
{
m_clientSocket.Send(packet);
}

}


It works great ,so i googled
c++ client code tcp
and i found this URL

https://msdn.microsoft.com/en-us/library/windows/desktop/ms737591%28v=vs.85%29.aspx


Here is the above url code

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>


// Need to link with Ws2_32.lib, Mswsock.lib, and Advapi32.lib
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")


#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"

int __cdecl main(int argc, char **argv)
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
char *sendbuf = "this is a test";
char recvbuf[DEFAULT_BUFLEN];
int iResult;
int recvbuflen = DEFAULT_BUFLEN;

// Validate the parameters
if (argc != 2) {
printf("usage: %s server-name\n", argv[0]);
return 1;
}

// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}

ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;

// Resolve the server address and port
iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
if (iResult != 0) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}

// Attempt to connect to an address until one succeeds
for (ptr = result; ptr != NULL; ptr = ptr->ai_next) {

// Create a SOCKET for connecting to server
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype,
ptr->ai_protocol);
if (ConnectSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
WSACleanup();
return 1;
}

// Connect to server.
iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
if (iResult == SOCKET_ERROR) {
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
continue;
}
break;
}

freeaddrinfo(result);

if (ConnectSocket == INVALID_SOCKET) {
printf("Unable to connect to server!\n");
WSACleanup();
return 1;
}

// Send an initial buffer
iResult = send(ConnectSocket, sendbuf, (int)strlen(sendbuf), 0);
if (iResult == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}

printf("Bytes Sent: %ld\n", iResult);

// shutdown the connection since no more data will be sent
iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}

// Receive until the peer closes the connection
do {

iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
if (iResult > 0)
printf("Bytes received: %d\n", iResult);
else if (iResult == 0)
printf("Connection closed\n");
else
printf("recv failed with error: %d\n", WSAGetLastError());

} while (iResult > 0);

// cleanup
closesocket(ConnectSocket);
WSACleanup();

return 0;
}


But the problem is i don't know which parts of this code are
IP
and
Port
?As you can see in my c# application i config the
IP
and
port
.But here in c++ code i can't find any variable to initialize the
IP
and
Port

Answer

Your code appears to loop through a sequence of available ports initially set up by the line :

iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);

& then looped through here

for (ptr = result; ptr != NULL; ptr = ptr->ai_next)

with an attempt to make the connection at this line

iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);

The IP & port values are stored in the struct pointed to by the ai_addr field of the addrinfo struct. The struct pointed to by ai_addr is protocol dependant - for TCP it is a sockaddr_in struct which contains sin_port & sin_addr which is another struct of 4 bytes for the IP address. See the following links :

https://msdn.microsoft.com/en-gb/library/windows/desktop/ms737530(v=vs.85).aspx https://msdn.microsoft.com/en-gb/library/windows/desktop/ms740496(v=vs.85).aspx https://msdn.microsoft.com/en-us/library/windows/desktop/ms738571(v=vs.85).aspx