Index: src/OFExceptions.h
==================================================================
--- src/OFExceptions.h
+++ src/OFExceptions.h
@@ -296,10 +296,20 @@
 /**
  * An OFException indicating an attempt to connect or bind an already connected
  * or bound socket 
  */
 @interface OFAlreadyConnectedException: OFException {}
+/**
+ * \return An error message for the exception as a C string.
+ */
+- (char*)cString;
+@end
+
+/**
+ * An OFException indicating that the specified port is invalid.
+ */
+@interface OFInvalidPortException: OFException
 /**
  * \return An error message for the exception as a C string.
  */
 - (char*)cString;
 @end

Index: src/OFExceptions.m
==================================================================
--- src/OFExceptions.m
+++ src/OFExceptions.m
@@ -320,8 +320,22 @@
 		return string;
 
 	asprintf(&string, "The socket of type %s is already connected or bound "
 	    "and thus can't be connected or bound again!", [object name]);
 
+	return string;
+}
+@end
+
+@implementation OFInvalidPortException
+- (char*)cString
+{
+	if (string != NULL)
+		return string;
+
+	asprintf(&string, "The port specified is not valid for a socket of "
+	    "type %s! This usually means you tried to use port 0, which is an "
+	    "invalid port.", [object name]);
+
 	return string;
 }
 @end

Index: src/OFTCPSocket.m
==================================================================
--- src/OFTCPSocket.m
+++ src/OFTCPSocket.m
@@ -59,14 +59,12 @@
      onPort: (uint16_t)port
 {
 	struct addrinfo hints, *res, *res0;
 	char portstr[6];
 
-	if (!port) {
-		/* FIXME: Throw exception */
-		return nil;
-	}
+	if (!port)
+		@throw [OFInvalidPortException newWithObject: self];
 
 	if (sock >= 0)
 		@throw [OFAlreadyConnectedException newWithObject: self];
 
 	memset(&hints, 0, sizeof(struct addrinfo));
@@ -109,14 +107,12 @@
   andFamily: (int)family
 {
 	struct addrinfo hints, *res;
 	char portstr[6];
 
-	if (!port) {
-		/* FIXME: Throw exception */
-		return nil;
-	}
+	if (!port)
+		@throw [OFInvalidPortException newWithObject: self];
 
 	if (sock >= 0)
 		@throw [OFAlreadyConnectedException newWithObject: self];
 
 	if ((sock = socket(family, SOCK_STREAM, 0)) < 0) {