Involved Source Filesclient.godebug.go Package rpc provides access to the exported methods of an object across a
network or other I/O connection. A server registers an object, making it visible
as a service with the name of the type of the object. After registration, exported
methods of the object will be accessible remotely. A server may register multiple
objects (services) of different types but it is an error to register multiple
objects of the same type.
Only methods that satisfy these criteria will be made available for remote access;
other methods will be ignored:
- the method's type is exported.
- the method is exported.
- the method has two arguments, both exported (or builtin) types.
- the method's second argument is a pointer.
- the method has return type error.
In effect, the method must look schematically like
func (t *T) MethodName(argType T1, replyType *T2) error
where T1 and T2 can be marshaled by encoding/gob.
These requirements apply even if a different codec is used.
(In the future, these requirements may soften for custom codecs.)
The method's first argument represents the arguments provided by the caller; the
second argument represents the result parameters to be returned to the caller.
The method's return value, if non-nil, is passed back as a string that the client
sees as if created by [errors.New]. If an error is returned, the reply parameter
will not be sent back to the client.
The server may handle requests on a single connection by calling [ServeConn]. More
typically it will create a network listener and call [Accept] or, for an HTTP
listener, [HandleHTTP] and [http.Serve].
A client wishing to use the service establishes a connection and then invokes
[NewClient] on the connection. The convenience function [Dial] ([DialHTTP]) performs
both steps for a raw network connection (an HTTP connection). The resulting
[Client] object has two methods, [Call] and Go, that specify the service and method to
call, a pointer containing the arguments, and a pointer to receive the result
parameters.
The Call method waits for the remote call to complete while the Go method
launches the call asynchronously and signals completion using the Call
structure's Done channel.
Unless an explicit codec is set up, package [encoding/gob] is used to
transport the data.
Here is a simple example. A server wishes to export an object of type Arith:
package server
import "errors"
type Args struct {
A, B int
}
type Quotient struct {
Quo, Rem int
}
type Arith int
func (t *Arith) Multiply(args *Args, reply *int) error {
*reply = args.A * args.B
return nil
}
func (t *Arith) Divide(args *Args, quo *Quotient) error {
if args.B == 0 {
return errors.New("divide by zero")
}
quo.Quo = args.A / args.B
quo.Rem = args.A % args.B
return nil
}
The server calls (for HTTP service):
arith := new(Arith)
rpc.Register(arith)
rpc.HandleHTTP()
l, err := net.Listen("tcp", ":1234")
if err != nil {
log.Fatal("listen error:", err)
}
go http.Serve(l, nil)
At this point, clients can see a service "Arith" with methods "Arith.Multiply" and
"Arith.Divide". To invoke one, a client first dials the server:
client, err := rpc.DialHTTP("tcp", serverAddress + ":1234")
if err != nil {
log.Fatal("dialing:", err)
}
Then it can make a remote call:
// Synchronous call
args := &server.Args{7,8}
var reply int
err = client.Call("Arith.Multiply", args, &reply)
if err != nil {
log.Fatal("arith error:", err)
}
fmt.Printf("Arith: %d*%d=%d", args.A, args.B, reply)
or
// Asynchronous call
quotient := new(Quotient)
divCall := client.Go("Arith.Divide", args, quotient, nil)
replyCall := <-divCall.Done // will be equal to divCall
// check errors, print, etc.
A server implementation will often provide a simple, type-safe wrapper for the
client.
The net/rpc package is frozen and is not accepting new features.
Package-Level Type Names (total 8)
/* sort by: | */
Call represents an active RPC. // The argument to the function (*struct). // Receives *Call when Go is complete. // After completion, the error status. // The reply from the function (*struct). // The name of the service and method to call.
func (*Client).Go(serviceMethod string, args any, reply any, done chan *Call) *Call
func (*Client).Go(serviceMethod string, args any, reply any, done chan *Call) *Call
Client represents an RPC Client.
There may be multiple outstanding Calls associated
with a single Client, and a Client may be used by
multiple goroutines simultaneously. Call invokes the named function, waits for it to complete, and returns its error status. Close calls the underlying codec's Close method. If the connection is already
shutting down, [ErrShutdown] is returned. Go invokes the function asynchronously. It returns the [Call] structure representing
the invocation. The done channel will signal when the call is complete by returning
the same Call object. If done is nil, Go will allocate a new channel.
If non-nil, done must be buffered or Go will deliberately crash.
*Client : io.Closer
func Dial(network, address string) (*Client, error)
func DialHTTP(network, address string) (*Client, error)
func DialHTTPPath(network, address, path string) (*Client, error)
func NewClient(conn io.ReadWriteCloser) *Client
func NewClientWithCodec(codec ClientCodec) *Client
func net/rpc/jsonrpc.Dial(network, address string) (*Client, error)
func net/rpc/jsonrpc.NewClient(conn io.ReadWriteCloser) *Client
Request is a header written before every RPC call. It is used internally
but documented here as an aid to debugging, such as when analyzing
network traffic. // sequence number chosen by client // format: "Service.Method"
func ClientCodec.WriteRequest(*Request, any) error
func ServerCodec.ReadRequestHeader(*Request) error
Response is a header written before every RPC return. It is used internally
but documented here as an aid to debugging, such as when analyzing
network traffic. // error, if any. // echoes that of the request // echoes that of the Request
func ClientCodec.ReadResponseHeader(*Response) error
func ServerCodec.WriteResponse(*Response, any) error
Server represents an RPC Server. Accept accepts connections on the listener and serves requests
for each incoming connection. Accept blocks until the listener
returns a non-nil error. The caller typically invokes Accept in a
go statement. HandleHTTP registers an HTTP handler for RPC messages on rpcPath,
and a debugging handler on debugPath.
It is still necessary to invoke [http.Serve](), typically in a go statement. Register publishes in the server the set of methods of the
receiver value that satisfy the following conditions:
- exported method of exported type
- two arguments, both of exported type
- the second argument is a pointer
- one return value, of type error
It returns an error if the receiver is not an exported type or has
no suitable methods. It also logs the error using package log.
The client accesses each method using a string of the form "Type.Method",
where Type is the receiver's concrete type. RegisterName is like [Register] but uses the provided name for the type
instead of the receiver's concrete type. ServeCodec is like [ServeConn] but uses the specified codec to
decode requests and encode responses. ServeConn runs the server on a single connection.
ServeConn blocks, serving the connection until the client hangs up.
The caller typically invokes ServeConn in a go statement.
ServeConn uses the gob wire format (see package gob) on the
connection. To use an alternate codec, use [ServeCodec].
See [NewClient]'s comment for information about concurrent access. ServeHTTP implements an [http.Handler] that answers RPC requests. ServeRequest is like [ServeCodec] but synchronously serves a single request.
It does not close the codec upon completion.
*Server : net/http.Handler
func NewServer() *Server
var DefaultServer *Server
ServerError represents an error that has been returned from
the remote side of the RPC connection.( ServerError) Error() string
ServerError : error
Package-Level Functions (total 13)
Accept accepts connections on the listener and serves requests
to [DefaultServer] for each incoming connection.
Accept blocks; the caller typically invokes it in a go statement.
Dial connects to an RPC server at the specified network address.
DialHTTP connects to an HTTP RPC server at the specified network address
listening on the default HTTP RPC path.
DialHTTPPath connects to an HTTP RPC server
at the specified network address and path.
NewClient returns a new [Client] to handle requests to the
set of services at the other end of the connection.
It adds a buffer to the write side of the connection so
the header and payload are sent as a unit.
The read and write halves of the connection are serialized independently,
so no interlocking is required. However each half may be accessed
concurrently so the implementation of conn should protect against
concurrent reads or concurrent writes.
NewClientWithCodec is like [NewClient] but uses the specified
codec to encode requests and decode responses.
Register publishes the receiver's methods in the [DefaultServer].
RegisterName is like [Register] but uses the provided name for the type
instead of the receiver's concrete type.
ServeCodec is like [ServeConn] but uses the specified codec to
decode requests and encode responses.
ServeConn runs the [DefaultServer] on a single connection.
ServeConn blocks, serving the connection until the client hangs up.
The caller typically invokes ServeConn in a go statement.
ServeConn uses the gob wire format (see package gob) on the
connection. To use an alternate codec, use [ServeCodec].
See [NewClient]'s comment for information about concurrent access.
ServeRequest is like [ServeCodec] but synchronously serves a single request.
It does not close the codec upon completion.
Package-Level Variables (total 2)
DefaultServer is the default instance of [*Server].
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