setsockopt function

The setsockopt function sets a socket option.

Syntax

int setsockopt(
  SOCKET     s,
  int        level,
  int        optname,
  const char *optval,
  int        optlen
);

Parameters

s

A descriptor that identifies a socket.

level

The level at which the option is defined (for example, SOL_SOCKET).

optname

The socket option for which the value is to be set (for example, SO_BROADCAST). The optname parameter must be a socket option defined within the specified level, or behavior is undefined.

optval

A pointer to the buffer in which the value for the requested option is specified.

optlen

The size, in bytes, of the buffer pointed to by the optval parameter.

Return Value

If no error occurs, setsockopt returns zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError.

Error code Meaning
WSANOTINITIALISED
A successful WSAStartup call must occur before using this function.
WSAENETDOWN
The network subsystem has failed.
WSAEFAULT
The buffer pointed to by the optval parameter is not in a valid part of the process address space or the optlen parameter is too small.
WSAEINPROGRESS
A blocking Windows Sockets 1.1 call is in progress, or the service provider is still processing a callback function.
WSAEINVAL
The level parameter is not valid, or the information in the buffer pointed to by the optval parameter is not valid.
WSAENETRESET
The connection has timed out when SO_KEEPALIVE is set.
WSAENOPROTOOPT
The option is unknown or unsupported for the specified provider or socket (see SO_GROUP_PRIORITY limitations).
WSAENOTCONN
The connection has been reset when SO_KEEPALIVE is set.
WSAENOTSOCK
The descriptor is not a socket.

Remarks

The setsockopt function sets the current value for a socket option associated with a socket of any type, in any state. Although options can exist at multiple protocol levels, they are always present at the uppermost socket level. Options affect socket operations, such as whether expedited data (OOB data for example) is received in the normal data stream, and whether broadcast messages can be sent on the socket.

Note  If the setsockopt function is called before the bind function, TCP/IP options will not be checked by using TCP/IP until the bind occurs. In this case, the setsockopt function call will always succeed, but the bind function call can fail because of an early setsockopt call failing.
 
Note  If a socket is opened, a setsockopt call is made, and then a sendto call is made, Windows Sockets performs an implicit bind function call.
 
There are two types of socket options: Boolean options that enable or disable a feature or behavior, and options that require an integer value or structure. To enable a Boolean option, the optval parameter points to a nonzero integer. To disable the option optval points to an integer equal to zero. The optlen parameter should be equal to sizeof(int) for Boolean options. For other options, optval points to an integer or structure that contains the desired value for the option, and optlen is the length of the integer or structure.

The following tables list some of the common options supported by the setsockopt function. The Type column identifies the type of data addressed by optval parameter. The Description column provides some basic information about the socket option. For more complete lists of socket options and more detailed information (default values, for example), see the detailed topics under Socket Options.

level = SOL_SOCKET

Value Type Description
SO_BROADCAST BOOL Configures a socket for sending broadcast data.
SO_CONDITIONAL_ACCEPT BOOL Enables incoming connections are to be accepted or rejected by the application, not by the protocol stack.
SO_DEBUG BOOL Enables debug output. Microsoft providers currently do not output any debug information.
SO_DONTLINGER BOOL Does not block close waiting for unsent data to be sent. Setting this option is equivalent to setting SO_LINGER with l_onoff set to zero.
SO_DONTROUTE BOOL Sets whether outgoing data should be sent on interface the socket is bound to and not a routed on some other interface. This option is not supported on ATM sockets (results in an error).
SO_GROUP_PRIORITY int Reserved.
SO_KEEPALIVE BOOL Enables sending keep-alive packets for a socket connection. Not supported on ATM sockets (results in an error).
SO_LINGER LINGER Lingers on close if unsent data is present.
SO_OOBINLINE BOOL Indicates that out-of-bound data should be returned in-line with regular data. This option is only valid for connection-oriented protocols that support out-of-band data. For a discussion of this topic, see Protocol Independent Out-Of-band Data.
SO_RCVBUF int Specifies the total per-socket buffer space reserved for receives.
SO_REUSEADDR BOOL Allows the socket to be bound to an address that is already in use. For more information, see bind. Not applicable on ATM sockets.
SO_EXCLUSIVEADDRUSE BOOL Enables a socket to be bound for exclusive access. Does not require administrative privilege.
SO_RCVTIMEO DWORD Sets the timeout, in milliseconds, for blocking receive calls.
SO_SNDBUF int Specifies the total per-socket buffer space reserved for sends.
SO_SNDTIMEO DWORD The timeout, in milliseconds, for blocking send calls.
SO_UPDATE_ACCEPT_CONTEXT int Updates the accepting socket with the context of the listening socket.
PVD_CONFIG Service Provider Dependent This object stores the configuration information for the service provider associated with socket s. The exact format of this data structure is service provider specific.
 

For more complete and detailed information about socket options for level = SOL_SOCKET, see SOL_SOCKET Socket Options.

level = IPPROTO_TCP

Value Type Description
TCP_NODELAY BOOL Disables the Nagle algorithm for send coalescing.This socket option is included for backward compatibility with Windows Sockets 1.1
 

For more complete and detailed information about socket options for level = IPPROTO_TCP, see IPPROTO_TCP Socket Options.

level = NSPROTO_IPX

Value Type Description
IPX_PTYPE int Sets the IPX packet type.
IPX_FILTERPTYPE int Sets the receive filter packet type
IPX_STOPFILTERPTYPE int Stops filtering the filter type set with IPX_FILTERTYPE
IPX_DSTYPE int Sets the value of the data stream field in the SPX header on every packet sent.
IPX_EXTENDED_ADDRESS BOOL Sets whether extended addressing is enabled.
IPX_RECVHDR BOOL Sets whether the protocol header is sent up on all receive headers.
IPX_RECEIVE_BROADCAST BOOL Indicates broadcast packets are likely on the socket. Set to TRUE by default. Applications that do not use broadcasts should set this to FALSE for better system performance.
IPX_IMMEDIATESPXACK BOOL Directs SPX connections not to delay before sending an ACK. Applications without back-and-forth traffic should set this to TRUE to increase performance.
 

For more complete and detailed information about socket options for level = NSPROTO_IPX, see NSPROTO_IPX Socket Options.

BSD options not supported for setsockopt are shown in the following table.

Value Type Description
SO_ACCEPTCONN BOOL Returns whether a socket is in listening mode. This option is only Valid for connection-oriented protocols. This socket option is not supported for the setting.
SO_RCVLOWAT int A socket option from BSD UNIX included for backward compatibility. This option sets the minimum number of bytes to process for socket input operations.
SO_SNDLOWAT int A socket option from BSD UNIX included for backward compatibility. This option sets the minimum number of bytes to process for socket output operations.
SO_TYPE int Returns the socket type for the given socket (SOCK_STREAM or SOCK_DGRAM, for example This socket option is not supported for the setting the socket type.
 
Note  When issuing a blocking Winsock call such as setsockopt, Winsock may need to wait for a network event before the call can complete. Winsock performs an alertable wait in this situation, which can be interrupted by an asynchronous procedure call (APC) scheduled on the same thread. Issuing another blocking Winsock call inside an APC that interrupted an ongoing blocking Winsock call on the same thread will lead to undefined behavior, and must never be attempted by Winsock clients.
 

Example Code

The following example demonstrates the setsockopt function.
C++
#ifndef UNICODE
#define UNICODE
#endif

#ifndef WIN32_LEAN_AND_MEAN #define WIN32_LEAN_AND_MEAN #endif

#include <winsock2.h> #include <Ws2tcpip.h> #include <stdio.h>

// Link with ws2_32.lib #pragma comment(lib, "Ws2_32.lib")

int main() {

//---------------------------------------
// Declare variables
WSADATA wsaData;

SOCKET ListenSocket;
sockaddr_in service;

int iResult = 0;

BOOL bOptVal = FALSE;
int bOptLen = sizeof (BOOL);

int iOptVal = 0;
int iOptLen = sizeof (int);

//---------------------------------------
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2, 2), &amp;wsaData);
if (iResult != NO_ERROR) {
    wprintf(L"Error at WSAStartup()\n");
    return 1;
}
//---------------------------------------
// Create a listening socket
ListenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (ListenSocket == INVALID_SOCKET) {
    wprintf(L"socket function failed with error: %u\n", WSAGetLastError());
    WSACleanup();
    return 1;
}
//---------------------------------------
// Bind the socket to the local IP address
// and port 27015
hostent *thisHost;
char *ip;
u_short port;
port = 27015;
thisHost = gethostbyname("");
ip = inet_ntoa(*(struct in_addr *) *thisHost-&gt;h_addr_list);

service.sin_family = AF_INET;
service.sin_addr.s_addr = inet_addr(ip);
service.sin_port = htons(port);

iResult = bind(ListenSocket, (SOCKADDR *) &amp; service, sizeof (service));
if (iResult == SOCKET_ERROR) {
    wprintf(L"bind failed with error %u\n", WSAGetLastError());
    closesocket(ListenSocket);
    WSACleanup();
    return 1;
}
//---------------------------------------
// Initialize variables and call setsockopt. 
// The SO_KEEPALIVE parameter is a socket option 
// that makes the socket send keepalive messages
// on the session. The SO_KEEPALIVE socket option
// requires a boolean value to be passed to the
// setsockopt function. If TRUE, the socket is
// configured to send keepalive messages, if FALSE
// the socket configured to NOT send keepalive messages.
// This section of code tests the setsockopt function
// by checking the status of SO_KEEPALIVE on the socket
// using the getsockopt function.

bOptVal = TRUE;

iResult = getsockopt(ListenSocket, SOL_SOCKET, SO_KEEPALIVE, (char *) &amp;iOptVal, &amp;iOptLen);
if (iResult == SOCKET_ERROR) {
    wprintf(L"getsockopt for SO_KEEPALIVE failed with error: %u\n", WSAGetLastError());
} else
    wprintf(L"SO_KEEPALIVE Value: %ld\n", iOptVal);

iResult = setsockopt(ListenSocket, SOL_SOCKET, SO_KEEPALIVE, (char *) &amp;bOptVal, bOptLen);
if (iResult == SOCKET_ERROR) {
    wprintf(L"setsockopt for SO_KEEPALIVE failed with error: %u\n", WSAGetLastError());
} else
    wprintf(L"Set SO_KEEPALIVE: ON\n");

iResult = getsockopt(ListenSocket, SOL_SOCKET, SO_KEEPALIVE, (char *) &amp;iOptVal, &amp;iOptLen);
if (iResult == SOCKET_ERROR) {
    wprintf(L"getsockopt for SO_KEEPALIVE failed with error: %u\n", WSAGetLastError());
} else
    wprintf(L"SO_KEEPALIVE Value: %ld\n", iOptVal);

closesocket(ListenSocket);
WSACleanup();
return 0;

}

Notes for IrDA Sockets

When developing applications using Windows sockets for IrDA, note the following:

  • The Af_irda.h header file must be explicitly included.
  • IrDA provides the following socket option:
    Value Type Meaning
    IRLMP_IAS_SET *IAS_SET Sets IAS attributes
     

The IRLMP_IAS_SET socket option enables the application to set a single attribute of a single class in the local IAS. The application specifies the class to set, the attribute, and attribute type. The application is expected to allocate a buffer of the necessary size for the passed parameters.

IrDA provides an IAS database that stores IrDA-based information. Limited access to the IAS database is available through the Windows Sockets 2 interface, but such access is not normally used by applications, and exists primarily to support connections to non-Windows devices that are not compliant with the Windows Sockets 2 IrDA conventions.

The following structure, IAS_SET, is used with the IRLMP_IAS_SET setsockopt option to manage the local IAS database:

C++
// #include <Af_irda.h> for this struct

typedef struct _IAS_SET { u_char irdaClassName[IAS_MAX_CLASSNAME]; char irdaAttribName[IAS_MAX_ATTRIBNAME]; u_long irdaAttribType; union { LONG irdaAttribInt; struct { u_long Len; u_char OctetSeq[IAS_MAX_OCTET_STRING]; } irdaAttribOctetSeq; struct { u_long Len; u_long CharSet; u_char UsrStr[IAS_MAX_USER_STRING]; } irdaAttribUsrStr; } irdaAttribute; } IAS_SET, *PIAS_SET, FAR *LPIASSET;

The following structure, IAS_QUERY, is used with the IRLMP_IAS_QUERY setsockopt option to query a peer's IAS database:
C++
// #include <Af_irda.h> for this struct

typedef struct _WINDOWS_IAS_QUERY { u_char irdaDeviceID[4]; char irdaClassName[IAS_MAX_CLASSNAME]; char irdaAttribName[IAS_MAX_ATTRIBNAME]; u_long irdaAttribType; union { LONG irdaAttribInt; struct { u_long Len; u_char OctetSeq[IAS_MAX_OCTET_STRING]; } irdaAttribOctetSeq; struct { u_long Len; u_long CharSet; u_char UsrStr[IAS_MAX_USER_STRING]; } irdaAttribUsrStr; } irdaAttribute; } IAS_QUERY, *PIAS_QUERY, FAR *LPIASQUERY;

Many SO_ level socket options are not meaningful to IrDA. Only SO_LINGER is specifically supported.

Windows Phone 8: This function is supported for Windows Phone Store apps on Windows Phone 8 and later.

Windows 8.1 and Windows Server 2012 R2: This function is supported for Windows Store apps on Windows 8.1, Windows Server 2012 R2, and later.

Requirements

   
Windows version Windows 8.1, Windows Vista [desktop apps UWP apps] Windows Server 2003 [desktop apps UWP apps]
Target Platform Windows
Header winsock.h (include Winsock2.h)
Library Ws2_32.lib
DLL Ws2_32.dll

See Also

IPPROTO_IP Socket Options

IPPROTO_IPV6 Socket Options

IPPROTO_RM Socket Options

IPPROTO_TCP Socket Options

IPPROTO_UDP Socket Options

NSPROTO_IPX Socket Options

SOL_APPLETALK Socket Options

SOL_IRLMP Socket Options

SOL_SOCKET Socket Options

Socket Options

WSAAsyncSelect

WSAEventSelect

WSAIoctl

Winsock Functions

bind

getsockopt

ioctlsocket

socket