TCP Client (Blocking)
// Simple TCP client using Winsock
#include <winsock2.h>
#include <ws2tcpip.h>
#pragma comment(lib, "ws2_32.lib")
int main() {
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
hints;
const char *sendbuf = "Hello from client";
char recvbuf[512];
int iResult, recvbuflen = 512;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed: %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("127.0.0.1", "27015", &hints, &result);
if ( iResult != 0 ) {
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
// Create a SOCKET for connecting to server
ConnectSocket = socket(result->ai_family, result->ai_socktype,
result->ai_protocol);
if (ConnectSocket == INVALID_SOCKET) {
printf("socket failed: %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Connect to server.
iResult = connect( ConnectSocket, result->ai_addr, (int)result->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 1;
}
// 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;
}
// Receive data until the server closes the connection
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());
// cleanup
closesocket(ConnectSocket);
WSACleanup();
return 0;
}
TCP Server (Asynchronous, Overlapped I/O)
// Asynchronous TCP server using Winsock overlapped I/O
#include <winsock2.h>
#include <ws2tcpip.h>
#include <windows.h>
#pragma comment(lib, "ws2_32.lib")
#define DEFAULT_PORT "27016"
#define BUFFER_SIZE 512
void CALLBACK WorkerRoutine(DWORD dwError, DWORD dwBytesTransferred,
LPWSAOVERLAPPED lpOverlapped, DWORD dwFlags) {
// This is invoked when an async operation completes
// For brevity, just close the connection
SOCKET client = *(SOCKET*)lpOverlapped->hEvent;
closesocket(client);
printf("Client disconnected (%d bytes transferred)\\n", dwBytesTransferred);
delete (SOCKET*)lpOverlapped->hEvent;
delete lpOverlapped;
}
int main() {
WSADATA wsaData;
SOCKET ListenSocket = INVALID_SOCKET, ClientSocket = INVALID_SOCKET;
struct addrinfo *result = NULL, hints;
int iResult;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed: %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; // use local address
// Resolve the server address and port
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if (iResult != 0) {
printf("getaddrinfo failed: %d\\n", iResult);
WSACleanup();
return 1;
}
// Create a socket for listening
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET) {
printf("socket failed: %ld\\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Bind the socket
iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("bind failed: %d\\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
// Listen for connections
iResult = listen(ListenSocket, SOMAXCONN);
if (iResult == SOCKET_ERROR) {
printf("listen failed: %d\\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
printf("Server listening on port %s\\n", DEFAULT_PORT);
while (TRUE) {
// Accept a client socket
ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET) {
printf("accept failed: %d\\n", WSAGetLastError());
break;
}
// Allocate overlapped structure and event handle
WSABUF wsaBuf;
char *recvbuf = new char[BUFFER_SIZE];
wsaBuf.buf = recvbuf;
wsaBuf.len = BUFFER_SIZE;
WSAOVERLAPPED *overlapped = new WSAOVERLAPPED{0};
overlapped->hEvent = (HANDLE)new SOCKET(ClientSocket);
// Issue asynchronous receive
DWORD flags = 0, recvBytes = 0;
iResult = WSARecv(ClientSocket, &wsaBuf, 1, &recvBytes, &flags,
overlapped, WorkerRoutine);
if (iResult == SOCKET_ERROR && WSAGetLastError() != WSA_IO_PENDING) {
printf("WSARecv failed: %d\\n", WSAGetLastError());
delete[] recvbuf;
delete overlapped;
closesocket(ClientSocket);
} else {
printf("Client connected, async receive posted\\n");
}
}
// Cleanup
closesocket(ListenSocket);
WSACleanup();
return 0;
}
UDP Echo Server
// UDP echo server example
#include <winsock2.h>
#include <ws2tcpip.h>
#pragma comment(lib, "ws2_32.lib")
#define SERVER_PORT "27017"
#define BUF_SIZE 512
int main() {
WSADATA wsaData;
SOCKET sock = INVALID_SOCKET;
struct addrinfo *result = NULL, hints;
char recvbuf[BUF_SIZE];
struct sockaddr_storage clientAddr;
int clientAddrLen = sizeof(clientAddr);
int iResult;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed: %d\\n", iResult);
return 1;
}
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET; // IPv4
hints.ai_socktype = SOCK_DGRAM;
hints.ai_protocol = IPPROTO_UDP;
hints.ai_flags = AI_PASSIVE;
// Resolve address
iResult = getaddrinfo(NULL, SERVER_PORT, &hints, &result);
if (iResult != 0) {
printf("getaddrinfo failed: %d\\n", iResult);
WSACleanup();
return 1;
}
// Create socket
sock = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (sock == INVALID_SOCKET) {
printf("socket failed: %ld\\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Bind socket
iResult = bind(sock, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("bind failed: %d\\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(sock);
WSACleanup();
return 1;
}
freeaddrinfo(result);
printf("UDP echo server listening on port %s\\n", SERVER_PORT);
while (TRUE) {
iResult = recvfrom(sock, recvbuf, BUF_SIZE, 0,
(SOCKADDR *)&clientAddr, &clientAddrLen);
if (iResult == SOCKET_ERROR) {
printf("recvfrom failed: %d\\n", WSAGetLastError());
break;
}
// Echo back the same data
sendto(sock, recvbuf, iResult, 0,
(SOCKADDR *)&clientAddr, clientAddrLen);
}
// Cleanup
closesocket(sock);
WSACleanup();
return 0;
}