Index: src/exceptions/OFAcceptFailedException.m
==================================================================
--- src/exceptions/OFAcceptFailedException.m
+++ src/exceptions/OFAcceptFailedException.m
@@ -71,8 +71,12 @@
 	OF_GETTER(_socket, false)
 }
 
 - (int)errNo
 {
+#ifdef _WIN32
+	return of_wsaerr_to_errno(_errNo);
+#else
 	return _errNo;
+#endif
 }
 @end

Index: src/exceptions/OFAddressTranslationFailedException.m
==================================================================
--- src/exceptions/OFAddressTranslationFailedException.m
+++ src/exceptions/OFAddressTranslationFailedException.m
@@ -115,8 +115,12 @@
 	OF_GETTER(_socket, false)
 }
 
 - (int)errNo
 {
+#ifdef _WIN32
+	return of_wsaerr_to_errno(_errNo);
+#else
 	return _errNo;
+#endif
 }
 @end

Index: src/exceptions/OFBindFailedException.m
==================================================================
--- src/exceptions/OFBindFailedException.m
+++ src/exceptions/OFBindFailedException.m
@@ -95,8 +95,12 @@
 	OF_GETTER(_socket, false)
 }
 
 - (int)errNo
 {
+#ifdef _WIN32
+	return of_wsaerr_to_errno(_errNo);
+#else
 	return _errNo;
+#endif
 }
 @end

Index: src/exceptions/OFConnectionFailedException.m
==================================================================
--- src/exceptions/OFConnectionFailedException.m
+++ src/exceptions/OFConnectionFailedException.m
@@ -96,8 +96,12 @@
 	OF_GETTER(_socket, false)
 }
 
 - (int)errNo
 {
+#ifdef _WIN32
+	return of_wsaerr_to_errno(_errNo);
+#else
 	return _errNo;
+#endif
 }
 @end

Index: src/exceptions/OFException.h
==================================================================
--- src/exceptions/OFException.h
+++ src/exceptions/OFException.h
@@ -19,10 +19,51 @@
 @class OFString;
 @class OFArray;
 @class OFMutableArray;
 
 #define OF_BACKTRACE_SIZE 32
+
+#if defined(_WIN32) && defined(OF_HAVE_SOCKETS)
+# define EADDRINUSE WSAEADDRINUSE
+# define EADDRNOTAVAIL WSAEADDRNOTAVAIL
+# define EAFNOSUPPORT WSAEAFNOSUPPORT
+# define EALREADY WSAEALREADY
+# define ECONNABORTED WSAECONNABORTED
+# define ECONNABORTED WSAECONNABORTED
+# define ECONNREFUSED WSAECONNREFUSED
+# define ECONNRESET WSAECONNRESET
+# define ECONNRESET WSAECONNRESET
+# define EDESTADDRREQ WSAEDESTADDRREQ
+# define EDQUOT WSAEDQUOT
+# define EHOSTDOWN WSAEHOSTDOWN
+# define EHOSTUNREACH WSAEHOSTUNREACH
+# define EINPROGRESS WSAEINPROGRESS
+# define EISCONN WSAEISCONN
+# define ELOOP WSAELOOP
+# define EMSGSIZE WSAEMSGSIZE
+# define ENETDOWN WSAENETDOWN
+# define ENETRESET WSAENETRESET
+# define ENETUNREACH WSAENETUNREACH
+# define ENOBUFS WSAENOBUFS
+# define ENOPROTOOPT WSAENOPROTOOPT
+# define ENOTCONN WSAENOTCONN
+# define ENOTSOCK WSAENOTSOCK
+# define EOPNOTSUPP WSAEOPNOTSUPP
+# define EPFNOSUPPORT WSAEPFNOSUPPORT
+# define EPROCLIM WSAEPROCLIM
+# define EPROTONOSUPPORT WSAEPROTONOSUPPORT
+# define EPROTOTYPE WSAEPROTOTYPE
+# define EREMOTE WSAEREMOTE
+# define ESHUTDOWN WSAESHUTDOWN
+# define ESOCKTNOSUPPORT WSAESOCKTNOSUPPORT
+# define ESTALE WSAESTALE
+# define ETIMEDOUT WSAETIMEDOUT
+# define ETOOMANYREFS WSAETOOMANYREFS
+# define EUSERS WSAEUSERS
+# define EWOULDBLOCK WSAEWOULDBLOCK
+extern int of_wsaerr_to_errno(int);
+#endif
 
 /*!
  * @brief The base class for all exceptions in ObjFW
  *
  * The OFException class is the base class for all exceptions in ObjFW, except

Index: src/exceptions/OFException.m
==================================================================
--- src/exceptions/OFException.m
+++ src/exceptions/OFException.m
@@ -27,10 +27,15 @@
 #import "OFException.h"
 #import "OFString.h"
 #import "OFArray.h"
 
 #import "autorelease.h"
+
+#ifdef _WIN32
+# include <errno.h>
+# include <winerror.h>
+#endif
 
 struct _Unwind_Context;
 typedef enum {
 	_URC_OK		  = 0,
 	_URC_END_OF_STACK = 5
@@ -66,10 +71,39 @@
 		return _URC_OK;
 	}
 
 	return _URC_END_OF_STACK;
 }
+
+#if defined(_WIN32) && defined(OF_HAVE_SOCKETS)
+int
+of_wsaerr_to_errno(int wsaerr)
+{
+	switch (wsaerr) {
+	case WSAEACCES:
+		return EACCES;
+	case WSAEBADF:
+		return EBADF;
+	case WSAEDISCON:
+		return EPIPE;
+	case WSAEFAULT:
+		return EFAULT;
+	case WSAEINTR:
+		return EINTR;
+	case WSAEINVAL:
+		return EINVAL;
+	case WSAENAMETOOLONG:
+		return ENAMETOOLONG;
+	case WSAENOTEMPTY:
+		return ENOTEMPTY;
+	case WSAEWOULDBLOCK:
+		return EAGAIN;
+	default:
+		return wsaerr;
+	}
+}
+#endif
 
 @implementation OFException
 + (instancetype)exception
 {
 	return [[[self alloc] init] autorelease];

Index: src/exceptions/OFListenFailedException.m
==================================================================
--- src/exceptions/OFListenFailedException.m
+++ src/exceptions/OFListenFailedException.m
@@ -80,8 +80,12 @@
 	return _backLog;
 }
 
 - (int)errNo
 {
+#ifdef _WIN32
+	return of_wsaerr_to_errno(_errNo);
+#else
 	return _errNo;
+#endif
 }
 @end

Index: src/exceptions/OFReadOrWriteFailedException.m
==================================================================
--- src/exceptions/OFReadOrWriteFailedException.m
+++ src/exceptions/OFReadOrWriteFailedException.m
@@ -89,8 +89,12 @@
 	return _requestedLength;
 }
 
 - (int)errNo
 {
+#ifdef _WIN32
+	return of_wsaerr_to_errno(_errNo);
+#else
 	return _errNo;
+#endif
 }
 @end