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So I wanted to learn more on how the TCP protocol works and started messing with windows sockets (WinSocks2), I managed to write a basic server and client from the Microsoft documentation.
I expected to see a 3-way handshake in Wireshark, and I did but not in the way I imagined, it was actually duplicated (The server sends the same packets as the client back to the client).
So my question is, is this normal, or am I doing something wrong?
Here is my source code of the server:
// This should be placed before #include <Windows.h> if the windows include is used
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <cstdio>
#include <Windows.h>
#include <WinSock2.h>
#include <WS2tcpip.h>
/// TEST CODE /// REMOVE AFTER TESTING WAS DONE ///
int main()
{
WSADATA wsaData;
int iResult;
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct addrinfo* result = NULL, * ptr = NULL, hints;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the local address and port to be used by the server
iResult = getaddrinfo("0.0.0.0", "1337", &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ListenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (ListenSocket == INVALID_SOCKET)
{
printf("Error at socket(): %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
}
iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR)
{
printf("bind failed with error: %d\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
if (listen(ListenSocket, SOMAXCONN) == SOCKET_ERROR)
{
printf("Listen failed with error: %ld\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// Handling pending connections
puts("Waiting for a connection..");
SOCKET ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET)
{
printf("accept failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
#define DEFAULT_BUFLEN 512
char recvbuf[DEFAULT_BUFLEN];
int iSendResult;
int recvbuflen = DEFAULT_BUFLEN;
int size =0 ;
// Receive until the peer shuts down the connection
do
{
iResult = recv(ClientSocket, recvbuf, recvbuflen, 0);
if (iResult > 0)
{
printf("Bytes received: %d\n", iResult);
size += iResult;
// I thought this was the problem but after I removed it from the code it still was the same.
//
// Echo the buffer back to the sender
//iSendResult = send(ClientSocket, recvbuf, iResult, 0);
/*if (iSendResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}*/
//printf("Bytes sent: %d\n", iSendResult);
}
else if (iResult == 0)
printf("Connection closing...\n");
else
{
printf("recv failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
}
while (iResult > 0);
recvbuf[size] = 0;
printf("Data received: %s\n", recvbuf);
// Stops responding to requests, still can accept tho
iResult = shutdown(ClientSocket, SD_SEND);
if (iResult == SOCKET_ERROR)
{
printf("shutdown failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
// Close socket, no receiving/sending
closesocket(ClientSocket);
WSACleanup();
}
And here is the client:
// This should be placed before #include <Windows.h> if the windows include is used
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <cstdio>
#include <Windows.h>
#include <WinSock2.h>
#include <WS2tcpip.h>
/// TEST CODE /// REMOVE AFTER TESTING WAS DONE ///
int main()
{
WSADATA wsaData;
int iResult;
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct addrinfo* result = NULL, * ptr = NULL, hints;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the local address and port to be used by the server
iResult = getaddrinfo("109.xxx.xxx.xxx", "1337", &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (ConnectSocket == INVALID_SOCKET)
{
printf("Error at socket(): %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
}
iResult = connect(ConnectSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR)
{
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
}
// Should really try the next address returned by getaddrinfo
// if the connect call failed
// But for this simple example we just free the resources
// returned by getaddrinfo and print an error message
freeaddrinfo(result);
if (ConnectSocket == INVALID_SOCKET)
{
printf("Unable to connect to server!\n");
WSACleanup();
return 1;
}
#define DEFAULT_BUFLEN 512
int recvbuflen = DEFAULT_BUFLEN;
const char* sendbuf = "this is a test";
char recvbuf[DEFAULT_BUFLEN];
// Send an initial buffer
iResult = send(ConnectSocket, sendbuf, (int)strlen(sendbuf), 0);
if (iResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
printf("Bytes Sent: %ld\n", iResult);
// shutdown the connection for sending since no more data will be sent
// the client can still use the ConnectSocket for receiving data
iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR)
{
printf("shutdown failed: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// Receive data until the server 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: %d\n", WSAGetLastError());
}
while (iResult > 0);
closesocket(ConnectSocket);
WSACleanup();
}
Here is the packets captured from Wireshark, where the IP address starting with 109.xxx.xxx.xxx is the server:
No, the duplicate packets are not normal. But that is not related to your code. It is more likely an issue with your network setup, or just a side effect of how you are capturing the packets.
Unrelated to the duplicate packets, there are other problems with the code shown.
In your server:
your if (ListenSocket == INVALID_SOCKET) block is missing a return, so if socket() fails then you still call bind() with an invalid SOCKET and are dereferencing an invalid result pointer.
Once you reach your recv() loop, you are never closing the ListenSocket before calling WSACleanup().
your printf() of recvbuf needs to be inside the loop when iResult > 0. And if you are going to null-terminate recvbuf then you need to use recvbuflen-1 when calling recv(), or else you will lose the last byte received. Otherwise, pass iResult as a parameter to printf() so you don't need to null-terminate recvbuf at all.
In your client:
do not use the AI_PASSIVE flag when calling getaddrinfo(). That flag is meant for listening servers, not outbound clients.
your if (ConnectSocket == INVALID_SOCKET) block is missing a return, so if socket() fails then you still call connect() with an invalid SOCKET and are dereferencing an invalid result pointer.
Try this code instead:
server:
// This should be placed before #include <Windows.h> if the windows include is used
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <cstdio>
#include <Windows.h>
#include <WinSock2.h>
#include <WS2tcpip.h>
/// TEST CODE /// REMOVE AFTER TESTING WAS DONE ///
int main()
{
WSADATA wsaData;
int iResult;
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct addrinfo* result = NULL, hints;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the local address and port to be used by the server
iResult = getaddrinfo(NULL, "1337", &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET)
{
printf("Error at socket(): %d\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR)
{
printf("bind failed with error: %d\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
if (listen(ListenSocket, SOMAXCONN) == SOCKET_ERROR)
{
printf("Listen failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// Handling pending connections
puts("Waiting for a connection..");
SOCKET ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET)
{
printf("accept failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
#define DEFAULT_BUFLEN 512
char recvbuf[DEFAULT_BUFLEN];
int iSendResult;
// Receive until the peer shuts down the connection
do
{
iResult = recv(ClientSocket, recvbuf, sizeof(recvbuf), 0);
if (iResult > 0)
{
printf("Bytes received: %d\n", iResult);
printf("Data received: %.*s\n", iResult, recvbuf);
// Echo the buffer back to the sender
/*iSendResult = send(ClientSocket, recvbuf, iResult, 0);
if (iSendResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
break;
}
printf("Bytes sent: %d\n", iSendResult);*/
}
else if (iResult == 0)
{
printf("Connection closing...\n");
}
else
{
printf("recv failed: %d\n", WSAGetLastError());
}
}
while (iResult > 0);
// Close socket, no receiving/sending
shutdown(ClientSocket, SD_BOTH);
closesocket(ClientSocket);
WSACleanup();
return 0;
}
client:
// This should be placed before #include <Windows.h> if the windows include is used
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <cstdio>
#include <Windows.h>
#include <WinSock2.h>
#include <WS2tcpip.h>
/// TEST CODE /// REMOVE AFTER TESTING WAS DONE ///
int main()
{
WSADATA wsaData;
int iResult;
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct addrinfo* result = NULL, hints;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
// Resolve the local address and port to be used by the server
iResult = getaddrinfo("109.xxx.xxx.xxx", "1337", &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ConnectSocket = INVALID_SOCKET;
for(struct addrinfo* ptr = result; ptr != NULL; ptr = ptr->ai_next)
{
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
if (ConnectSocket == INVALID_SOCKET)
{
printf("Error at socket(): %d\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
iResult = connect(ConnectSocket, result->ai_addr, (int)result->ai_addrlen);
freeaddrinfo(result);
if (iResult != SOCKET_ERROR)
break;
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
}
if (ConnectSocket == INVALID_SOCKET)
{
printf("Unable to connect to server!\n");
WSACleanup();
return 1;
}
#define DEFAULT_BUFLEN 512
const char* sendbuf = "this is a test";
char recvbuf[DEFAULT_BUFLEN];
// Send an initial buffer
iResult = send(ConnectSocket, sendbuf, (int)strlen(sendbuf), 0);
if (iResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
printf("Bytes Sent: %ld\n", iResult);
// shutdown the connection for sending since no more data will be sent
// the client can still use the ConnectSocket for receiving data
iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR)
{
printf("shutdown failed: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// Receive data until the server closes the connection
do
{
iResult = recv(ConnectSocket, recvbuf, sizeof(recvbuf), 0);
if (iResult > 0)
printf("Bytes received: %d\n", iResult);
else if (iResult == 0)
printf("Connection closed\n");
else
printf("recv failed: %d\n", WSAGetLastError());
}
while (iResult > 0);
shutdown(ConnectSocket, SD_RECEIVE);
closesocket(ConnectSocket);
WSACleanup();
return 0;
}
I'm currently using Winsock2 to be able to test a connection to multiple local telnet servers, but if the server connection fails, the default Winsock client takes forever to timeout.
I've seen from other posts that select() can set a timeout for the connection part, and that setsockopt() with timeval can timeout the receiving portion of the code, but I have no idea how to implement either. Pieces of code that I've copy/pasted from other answers always seem to fail for me.
How would I use both of these functions in the default client code? Or, if it isn't possible to use those functions in the default client code, can someone give me some pointers on how to use those functions correctly?
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <ctime>
// 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 "23"
int __cdecl main(int argc, char** argv)
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo* result = NULL,
* ptr = NULL,
hints;
const 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;
/*
struct timeval timeout;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
if (setsockopt(ConnectSocket, SOL_SOCKET, SO_RCVTIMEO, (char*)&timeout,
sizeof(timeout)) < 0) {
printf("setsockopt failed\n");
}
*/
// 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;
}
select() can set a timeout for the connection part.
Yes, but only if you put the socket into non-blocking mode before calling connect(), so that connect() exits immediately and then the code can use select() to wait for the socket to report when the connect operation has finished. But the code shown is not doing that.
setsockopt() with timeval can timeout the receiving portion of the code
Yes, though select() can also be used to timeout a read operation, as well. Simply call select() first, and then call recv() only if select() reports that the socket is readable (has pending data to read).
Try something like this:
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <ctime>
// 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 "23"
int __cdecl main(int argc, char** argv)
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
const 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;
}
// put the socket into non-blocking mode just for connect()
int iMode = 1;
iResult = ioctlsocket(ConnectSocket, FIONBIO, &iMode);
if (iResult == SOCKET_ERROR)
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
continue;
}
// Connect to server.
iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
if (iResult == SOCKET_ERROR) {
if (WSAGetLastError() != WSAEWOULDBLOCK) {
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
continue;
}
// wait for the connect to finish
fd_set fds;
FD_ZERO(&fds);
FD_SET(ConnectSocket, &fds);
struct timeval timeout;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
iResult = select(0, NULL, &fds, NULL, &timeout);
if (iResult <= 0) {
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
continue;
}
}
// put the socket back into blocking mode
iMode = 0;
iResult = ioctlsocket(ConnectSocket, FIONBIO, &iMode);
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;
}
struct timeval timeout;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
// set a read timeout
if (setsockopt(ConnectSocket, SOL_SOCKET, SO_RCVTIMEO, (char*)&timeout, sizeof(timeout)) == SOCKET_ERROR) {
printf("setsockopt failed\n");
}
// 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 {
/*
fd_set fds;
FD_ZERO(&fds);
FD_SET(ConnectSocket, &fds);
struct timeval timeout;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
iResult = select(0, &fds, NULL, NULL, &timeout);
if (iResult <= 0) {
if (iResult == SOCKET_ERROR)
printf("select failed with error: %d\n", WSAGetLastError());
else
printf("select timed out\n");
break;
}
*/
iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
if (iResult > 0)
printf("Bytes received: %d\n", iResult);
else if (iResult == 0)
printf("Connection closed\n");
else if (WSAGetLastError() == WSAETIMEDOUT)
printf("recv timed out\n");
else
printf("recv failed with error: %d\n", WSAGetLastError());
} while (iResult > 0);
// cleanup
closesocket(ConnectSocket);
WSACleanup();
return 0;
}
I am following this tutorial by MS to build a basic winsock application, problem is, both server and client compile OK however I am unable to make a connection since client simply disappears. I have VS 2017 15.7.5 installed with Windows 10 SDK (10.0.17134.0). Any ideas on what might be the problem??
Client code:
#include "stdafx.h"
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
using namespace std;
// 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;
const 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();
cin.get();
return 0;
}
Server code:
#include "stdafx.h"
#undef UNICODE
#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
#pragma comment (lib, "Ws2_32.lib")
// #pragma comment (lib, "Mswsock.lib")
#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"
int __cdecl main(void)
{
WSADATA wsaData;
int iResult;
SOCKET ListenSocket = INVALID_SOCKET;
SOCKET ClientSocket = INVALID_SOCKET;
struct addrinfo *result = NULL;
struct addrinfo hints;
int iSendResult;
char recvbuf[DEFAULT_BUFLEN];
int recvbuflen = DEFAULT_BUFLEN;
// 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_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the server address and port
iResult = getaddrinfo(NULL, DEFAULT_PORT, & hints, & result);
if (iResult != 0) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}
// Create a SOCKET for connecting to server
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Setup the TCP listening socket
iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("bind failed with error: %d\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
iResult = listen(ListenSocket, SOMAXCONN);
if (iResult == SOCKET_ERROR) {
printf("listen failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// Accept a client socket
ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET) {
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// No longer need server socket
closesocket(ListenSocket);
// Receive until the peer shuts down the connection
do {
iResult = recv(ClientSocket, recvbuf, recvbuflen, 0);
if (iResult > 0) {
printf("Bytes received: %d\n", iResult);
// Echo the buffer back to the sender
iSendResult = send(ClientSocket, recvbuf, iResult, 0);
if (iSendResult == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
printf("Bytes sent: %d\n", iSendResult);
}
else if (iResult == 0)
printf("Connection closing...\n");
else {
printf("recv failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
} while (iResult > 0);
// shutdown the connection since we're done
iResult = shutdown(ClientSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
// cleanup
closesocket(ClientSocket);
WSACleanup();
return 0;
}
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Code:
#define WIN32_LEAN_AND_MEAN
#include <WinSock2.h>
#include <WS2tcpip.h>
#include <iostream>
#include <string>
// link with Ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")
#define DEFAULT_PORT "27015"
#define DEFAULT_BUFFER_LENGTH 512
class Client {
public:
Client(char* servername)
{
szServerName = servername;
ConnectSocket = INVALID_SOCKET;
}
bool Start() {
WSADATA wsaData;
// Initialize Winsock
int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if(iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return false;
}
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
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(szServerName, DEFAULT_PORT, &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return false;
}
ptr = result;
// Create a SOCKET for connecting to server
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
if (ConnectSocket == INVALID_SOCKET)
{
printf("Error at socket(): %d\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return false;
}
// Connect to server
iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
if (iResult == SOCKET_ERROR)
{
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
}
freeaddrinfo(result);
if (ConnectSocket == INVALID_SOCKET)
{
printf("Unable to connect to server!\n");
WSACleanup();
return false;
}
return true;
};
// Free the resouces
void Stop() {
int iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR)
{
printf("shutdown failed: %d\n", WSAGetLastError());
}
closesocket(ConnectSocket);
WSACleanup();
};
// Send message to server
bool Send(char* szMsg)
{
int iResult = send(ConnectSocket, szMsg, strlen(szMsg), 0);
if (iResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
Stop();
return false;
}
return true;
};
// Receive message from server
bool Recv()
{
char recvbuf[DEFAULT_BUFFER_LENGTH];
int iResult = recv(ConnectSocket, recvbuf, DEFAULT_BUFFER_LENGTH, 0);
if (iResult > 0)
{
char msg[DEFAULT_BUFFER_LENGTH];
memset(&msg, 0, sizeof(msg));
strcpy_s(msg, recvbuf, iResult);
printf("Received: %s\n", msg);
return true;
}
return false;
}
private:
char* szServerName;
SOCKET ConnectSocket;
};
int main(int argc, CHAR* argv[])
{
std::string msg;
Client client("127.0.0.1");
if (!client.Start())
return 1;
while(true)
{
std::cout << "Send: ";
std::getline(std::cin, msg);
// Close the connection when user enter "close"
if (msg.compare("close") == 0)
{
break;
}
client.Send((char*)msg.c_str());
client.Recv();
}
client.Stop();
getchar();
return 0;
}
and
#define WIN32_LEAN_AND_MEAN
#include <WinSock2.h>
#include <WS2tcpip.h>
#include <stdio.h>
#include <stdlib.h>
// link with Ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")
#define DEFAULT_PORT "27015"
#define DEFAULT_BUFFER_LENGTH 512
int main() {
WSADATA wsaData;
// Initialize Winsock
int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if(iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct addrinfo *result = NULL,
hints;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET; // Internet address family is unspecified so that either an IPv6 or IPv4 address can be returned
hints.ai_socktype = SOCK_STREAM; // Requests the socket type to be a stream socket for the TCP protocol
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the local address and port to be used by the server
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ListenSocket = INVALID_SOCKET;
// Create a SOCKET for the server to listen for client connections
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET)
{
printf("Error at socket(): %d\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Setup the TCP listening socket
iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR)
{
printf("bind failed: %d", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
// To listen on a socket
if ( listen(ListenSocket, SOMAXCONN) == SOCKET_ERROR)
{
printf("listen failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
SOCKET ClientSocket;
ClientSocket = INVALID_SOCKET;
// Accept a client socket
ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET)
{
printf("accept failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
char recvbuf[DEFAULT_BUFFER_LENGTH];
int iSendResult;
// reveice until the client shutdown the connection
do {
iResult = recv(ClientSocket, recvbuf, DEFAULT_BUFFER_LENGTH, 0);
if (iResult > 0)
{
char msg[DEFAULT_BUFFER_LENGTH];
memset(&msg, 0, sizeof(msg));
strcpy_s(msg, recvbuf, iResult);
printf("Received: %s\n", msg);
iSendResult = send(ClientSocket, recvbuf, iResult, 0);
if (iSendResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
printf("Bytes sent: %ld\n", iSendResult);
}
else if (iResult == 0)
printf("Connection closed\n");
else
{
printf("recv failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
//return 1;
}
} while (iResult > 0);
// Free the resouces
closesocket(ListenSocket);
WSACleanup();
getchar();
return 0;
}
Errors:
error C2664: 'errno_t strcpy_s(char *,rsize_t,const char *)' : cannot
convert parameter 2 from 'char [512]' to 'rsize_t'
error C2664: 'errno_t strcpy_s(char *,rsize_t,const char *)' : cannot
convert parameter 2 from 'char [512]' to 'rsize_t'
IntelliSense: no instance of overloaded function "strcpy_s" matches
the argument list
argument types are: (char [512], char [512], int)
I have been trying to fix this problem. Please help.
New code:
#define WIN32_LEAN_AND_MEAN
#include <WinSock2.h>
#include <WS2tcpip.h>
#include <stdio.h>
#include <stdlib.h>
// link with Ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")
#define DEFAULT_PORT "27015"
#define DEFAULT_BUFFER_LENGTH 128
int main() {
WSADATA wsaData;
// Initialize Winsock
int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if(iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct addrinfo *result = NULL,
hints;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET; // Internet address family is unspecified so that either an IPv6 or IPv4 address can be returned
hints.ai_socktype = SOCK_STREAM; // Requests the socket type to be a stream socket for the TCP protocol
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the local address and port to be used by the server
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ListenSocket = INVALID_SOCKET;
// Create a SOCKET for the server to listen for client connections
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET)
{
printf("Error at socket(): %d\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Setup the TCP listening socket
iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR)
{
printf("bind failed: %d", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
// To listen on a socket
if ( listen(ListenSocket, SOMAXCONN) == SOCKET_ERROR)
{
printf("listen failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
SOCKET ClientSocket;
ClientSocket = INVALID_SOCKET;
// Accept a client socket
ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET)
{
printf("accept failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
char recvbuf[DEFAULT_BUFFER_LENGTH];
int iSendResult;
// reveice until the client shutdown the connection
do {
iResult = recv(ClientSocket, recvbuf, DEFAULT_BUFFER_LENGTH, 0);
if (iResult > 0)
{
char msg[DEFAULT_BUFFER_LENGTH];
memset(&msg, 0, sizeof(msg));
strcpy_s(msg, iResult, recvbuf);
printf("Received: %s\n", msg);
iSendResult = send(ClientSocket, recvbuf, iResult, 0);
if (iSendResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
printf("Bytes sent: %ld\n", iSendResult);
}
else if (iResult == 0)
printf("Connection closed\n");
else
{
printf("recv failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
//return 1;
}
} while (iResult > 0);
// Free the resouces
closesocket(ListenSocket);
WSACleanup();
getchar();
return 0;
}
New error:
http://i.stack.imgur.com/55IUF.png
You have the parameters in the wrong order.
errno_t strcpy_s(char *dest, rsize_t size, const char *src);
You put the src in the size param and the size in the src param.
I am very new to networking,i am trying to open a socket and get a file from a server.
I am getting connection timeout error 100060.
my code is:-
#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 != 1) {
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("74.125.236.83", 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);
printf("inside loop\n");
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);
printf("%d\n",ptr->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("socket error\n");
printf("shutdown failed with error: %d\n", WSAGetLastError());
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;
}
Have you tried using AF_INET instead of AF_UNSPEC?
Maybe you should printf() the values in results, especially ptr->ai_addr, to make sure the resolution went fine.
And obviously check that a server is listen()ing and accept()ing on the other side; did you prove it, with, for instance:
telnet 74.125.236.83:27015
In this line:
// Attempt to connect to an address until one succeeds
for(ptr=result; ptr != NULL ;ptr=ptr->ai_next) {
you are initializing ptr to result. But result is never being set to a value != NULL, so the loop exits immediately.
From your code, it seems to me that you meant:
// Attempt to connect to an address until one succeeds
for(ptr=hints; ptr != NULL ;ptr=ptr->ai_next) {