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Encoding for General Proxy Parameters

The encoding format of proxies changed in version 1.1.

Proxy Parameter Encoding version 1.0

The first component of an encoded proxy is a value of type Ice::Identity. If the proxy is a nil value, the category and name members are empty strings, and no additional data is encoded. The encoding for a non-null proxy consists of general parameters followed by endpoint parameters.

The general proxy parameters are encoded as if they were members of the following structure:

{zcode:slice}
struct ProxyData {
    Ice::Identity id;
    Ice::StringSeq facet;
    byte mode;
    bool secure;
};
{zcode}

The general proxy parameters are described in the table below:

The facet field has either zero elements or one element. An empty sequence denotes the default facet, and a one-element sequence provides the facet name in its first member. If a receiver receives a proxy with a facet field with more than one element, it must throw a ProxyUnmarshalException.

Proxy Parameter Encoding version 1.1

Version 1.1 of the encoding appends two attributes to the existing proxy parameters in version 1.0: protocol and encoding versions. The general proxy parameters are encoded as if they were members of the following structure:

{zcode:slice}
struct ProtocolVersion {
    byte major;
    byte minor;
};
 
struct EncodingVersion {
    byte major;
    byte minor;
};
struct ProxyData {
    Ice::Identity id;
    Ice::StringSeq facet;
    byte mode;
    bool secure;
    ProtocolVersion protocol;
    EncodingVersion encoding;
};
{zcode}

The additional parameters are described in the table below:

The encoding for UDP endpoints also changed in version 1.1.

Encoding for Endpoint Parameters

A proxy optionally contains an endpoint list or an adapter identifier, but not both:

• If a proxy contains endpoints, they are encoded immediately following the general parameters. A size specifying the number of endpoints is encoded first, followed by the endpoints. Each endpoint is encoded as a short specifying the endpoint type (1=TCP, 2=SSL, 3=UDP), followed by an encapsulation of type-specific parameters. The type-specific parameters for TCP, UDP, and SSL are presented in the sections that follow.
• If a proxy does not have endpoints, a single byte with value 0 immediately follows the general parameters and a string representing the object adapter identifier is encoded immediately following the zero byte.
• For a proxy to a well-known object, which has neither endpoints nor an object adapter identifier, a single byte with value 0 immediately follows the general parameters and an empty string is encoded immediately following the zero byte.

Type-specific endpoint parameters are encapsulated because a receiver may not be capable of decoding them. For example, a receiver can only decode SSL endpoint parameters if it is configured with the IceSSL plug-in. However, the receiver must be able to re-encode the proxy with all of its original endpoints, in the order they were received, even if the receiver does not understand the type-specific parameters for an endpoint. Encapsulation of the parameters into an opaque endpoint allows the receiver to do this.

Encoding for TCP Endpoint Parameters

A TCP endpoint is encoded as an encapsulation containing the following structure:

{zcode:slice}
struct TCPEndpointData {
    string host;
    int port;
    int timeout;
    bool compress;
};
{zcode}

The endpoint parameters are described in the following table.

Encoding for UDP Endpoint Parameters

The encoding format of UDP endpoints changed in version 1.1.

UDP Endpoint Encoding version 1.0

A UDP endpoint is encoded as an encapsulation containing the following structure:

{zcode:slice}
struct UDPEndpointData {
    string host;
    int port;
    byte protocolMajor;
    byte protocolMinor;
    byte encodingMajor;
    byte encodingMinor;
    bool compress;
};
{zcode}

The endpoint parameters are described in the following table.

UDP Endpoint Encoding version 1.1

Version 1.1 of the encoding omits the protocol and encoding versions because these attributes are handled as general proxy parameters instead:

{zcode:slice}
struct UDPEndpointData {
    string host;
    int port;
    bool compress;
};
{zcode}

The endpoint parameters are described in the following table.

Encoding for SSL Endpoint Parameters

An SSL endpoint is encoded as an encapsulation containing the following structure:

{zcode:slice}
struct SSLEndpointData {
    string host;
    int port;
    int timeout;
    bool compress;
};
{zcode}

The endpoint parameters are described in the following table.

See Also

• Object Identity
• Facets and Versioning
• Basic Data Encoding
• IceSSL
• Using Connections
• Protocol Compression