connect
Establishes a connection to a specified remote host and port.
Syntax
int connect(
SOCKET s,
const struct sockaddr *name,
int namelen
);
Parameters
| Parameter | Description |
|---|---|
s |
A descriptor identifying an unconnected socket. |
name |
A pointer to a sockaddr structure that specifies the destination address and port for the connection. |
namelen |
The size, in bytes, of the sockaddr structure pointed to by the name parameter. |
Return Value
If the connection is successfully established, connect returns zero. Otherwise, it returns SOCKET_ERROR, and a specific error code can be retrieved by calling WSAGetLastError.
Remarks
The connect function is used to establish a connection on a socket. For connection-oriented protocols, this is the explicit connection setup phase. For datagram sockets, this call is a permissible but not required operation. If used with a datagram socket, it specifies the default destination for send operations and the default destination for recv operations.
When a connect call is made on a connectionless socket (such as SOCK_DGRAM), the local transport provider is instructed to deliver datagrams only to the specified foreign host and port. Any datagrams sent to a different destination will be returned with a WSAECONNRESET error.
If the socket is non-blocking and the connection cannot be established immediately, connect will return WSAEWOULDBLOCK. The application can then use WSAAsyncSelect or WSAEventSelect to be notified when the connection is established (represented by the FD_CONNECT network event).
A connect call on a non-blocking socket will succeed if the connection can be established immediately. Otherwise, the call returns WSAEWOULDBLOCK.
Examples
The following example demonstrates how to use the connect function:
// Include Winsock header
#include <winsock2.h>
#include <ws2tcpip.h>
#pragma comment(lib, "Ws2_32.lib")
int main() {
WSADATA wsaData;
int iResult;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0) {
// Handle error
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
SOCKET ConnectSocket = INVALID_SOCKET;
struct sockaddr_in clientService;
// Create a SOCKET for connecting to server
ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (ConnectSocket == INVALID_SOCKET) {
// Handle error
printf("Error at socket(): %ld\n", WSAGetLastError());
WSACleanup();
return 1;
}
//----------------------------------------------------------------------------------
// The sockaddr_in structure specifies the address family,
// IP address, and port for the server to connect to.
//----------------------------------------------------------------------------------
clientService.sin_family = AF_INET;
clientService.sin_addr.s_addr = inet_addr("127.0.0.1"); // Replace with server IP
clientService.sin_port = htons(8080); // Replace with server port
//----------------------------------------------------------------------------------
// Connect to server.
//----------------------------------------------------------------------------------
iResult = connect(ConnectSocket, (SOCKADDR*)&clientService, sizeof(clientService));
if (iResult == SOCKET_ERROR) {
// Handle error
printf("connect failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// Connection successful
printf("Connected to server!\n");
// Send and receive data here...
// Close the socket
closesocket(ConnectSocket);
WSACleanup();
return 0;
}