/// <summary>
/// Create a request
/// </summary>
/// <remarks>
/// <para>
/// A valid SIP request formulated by a UAC MUST, at a minimum, contain
/// the following header fields: To, From, CSeq, Call-ID, Max-Forwards,
/// and Via; all of these header fields are mandatory in all SIP
/// requests. These six header fields are the fundamental building
/// blocks of a SIP message, as they jointly provide for most of the
/// critical message routing services including the addressing of
/// messages, the routing of responses, limiting message propagation,
/// ordering of messages, and the unique identification of transactions.
/// These header fields are in addition to the mandatory request line,
/// which contains the method, Request-URI, and SIP version.
/// <para></para>
/// Examples of requests sent outside of a dialog include an INVITE to
/// establish a session (RFC3261 - Section 13) and an OPTIONS to query for
/// capabilities (RFC3261 - Section 11).
/// </para>
/// <para>
/// Read section 8.1.1 in RFC3261 for more information
/// </para>
/// </remarks>
private IRequest CreateRequest(string method, Contact from, Contact to)
{
Request request = new Request(method, to.Uri, "SIP/2.0");
request.To = to;
request.From = from;
request.From.Parameters["tag"] = CreateRandomString(8);
request.CallId = method == SipMethod.REGISTER ? _registerCallId : CreateRandomString();
request.CSeq = new CSeq(GetNextSequenceNumber(), method);
request.MaxForwards = 70;
request.Contact = _contact;
if (_defaultRoute != null && _defaultRoute.Items.Count > 0)
request.Headers.Add(Route.ROUTE_NAME, (IHeader)_defaultRoute.Clone());
return request;
}
/// <summary>
/// Create a new request within this dialog.
/// </summary>
/// <returns>Created request.</returns>
/// <remarks>
/// <para>Described in RFC3261 Section 12.2.1.1 "Generating the Request".</para>
/// </remarks>
public IRequest CreateRequest(string method)
{
// The URI in the To field of the request MUST be set to the remote URI
// from the dialog state. The tag in the To header field of the request
// MUST be set to the remote tag of the dialog ID. The From URI of the
// request MUST be set to the local URI from the dialog state. The tag
// in the From header field of the request MUST be set to the local tag
// of the dialog ID. If the value of the remote or local tags is null,
// the tag parameter MUST be omitted from the To or From header fields,
// respectively.
// Usage of the URI from the To and From fields in the original
// request within subsequent requests is done for backwards
// compatibility with RFC 2543, which used the URI for dialog
// identification. In this specification, only the tags are used for
// dialog identification. It is expected that mandatory reflection
// of the original To and From URI in mid-dialog requests will be
// deprecated in a subsequent revision of this specification.
var request = new Request(method, RemoteUri, "SIP/2.0");
request.To.Uri = RemoteUri;
request.To.Parameters["tag"] = RemoteTag;
request.From.Uri = LocalUri;
request.From.Parameters["tag"] = LocalTag;
// The Call-ID of the request MUST be set to the Call-ID of the dialog.
// Requests within a dialog MUST contain strictly monotonically
// increasing and contiguous CSeq sequence numbers (increasing-by-one)
// in each direction (excepting ACK and CANCEL of course, whose numbers
// equal the requests being acknowledged or cancelled). Therefore, if
// the local sequence number is not empty, the value of the local
// sequence number MUST be incremented by one, and this value MUST be
// placed into the CSeq header field. If the local sequence number is
// empty, an initial value MUST be chosen using the guidelines of
// Section 8.1.1.5. The method field in the CSeq header field value
// MUST match the method of the request.
// With a length of 32 bits, a client could generate, within a single
// call, one request a second for about 136 years before needing to
// wrap around. The initial value of the sequence number is chosen
// so that subsequent requests within the same call will not wrap
// around. A non-zero initial value allows clients to use a time-
// based initial sequence number. A client could, for example,
// choose the 31 most significant bits of a 32-bit second clock as an
// initial sequence number.
request.CallId = CallId;
if (LocalSequenceNumber > 0)
{
LocalSequenceNumber += 1;
request.CSeq.Method = method;
request.CSeq.Number = LocalSequenceNumber;
}
// The UAC uses the remote target and route set to build the Request-URI
// and Route header field of the request.
// If the route set is empty, the UAC MUST place the remote target URI
// into the Request-URI. The UAC MUST NOT add a Route header field to
// the request.
if (RouteSet.Items.Count > 0)
{
// If the route set is not empty, and the first URI in the route set
// contains the lr parameter (see Section 19.1.1), the UAC MUST place
// the remote target URI into the Request-URI and MUST include a Route
// header field containing the route set values in order, including all
// parameters.
if (RouteSet.First.IsLoose)
{
request.Uri = RemoteTarget.FirstContact.Uri;
request.Headers[Route.ROUTE_NAME] = RouteSet;
}
// If the route set is not empty, and its first URI does not contain the
// lr parameter, the UAC MUST place the first URI from the route set
// into the Request-URI, stripping any parameters that are not allowed
// in a Request-URI. The UAC MUST add a Route header field containing
// the remainder of the route set values in order, including all
// parameters. The UAC MUST then place the remote target URI into the
// Route header field as the last value.
else
{
request.Uri = RouteSet.First.Uri; // not cloning since same routing will always be used.
request.Uri.Parameters.Remove("method");
var route = new Route(Route.ROUTE_NAME);
request.Headers.Add(Route.ROUTE_NAME, route);
for (int i = 1; i < RouteSet.Items.Count; ++i)
route.Items.Add(RouteSet.Items[i]);
route.Items.Add(new RouteEntry {Uri = RemoteTarget.FirstContact.Uri});
}
}
// A UAC SHOULD include a Contact header field in any target refresh
// requests within a dialog, and unless there is a need to change it,
// the URI SHOULD be the same as used in previous requests within the
// dialog. If the "secure" flag is true, that URI MUST be a SIPS URI.
// As discussed in Section 12.2.2, a Contact header field in a target
// refresh request updates the remote target URI. This allows a UA to
// provide a new contact address, should its address change during the
// duration of the dialog.
//request.Contact = Local
// However, requests that are not target refresh requests do not affect
// the remote target URI for the dialog.
// The rest of the request is formed as described in Section 8.1.1.
// Once the request has been constructed, the address of the server is
// computed and the request is sent, using the same procedures for
// requests outside of a dialog (Section 8.1.2).
// The procedures in Section 8.1.2 will normally result in the
// request being sent to the address indicated by the topmost Route
// header field value or the Request-URI if no Route header field is
// present. Subject to certain restrictions, they allow the request
// to be sent to an alternate address (such as a default outbound
// proxy not represented in the route set).
return request;
}