xmlrpc (3) - Linux Manuals


xmlrpc - XML-RPC library


This is an HTTP 1.1 compliant XML-RPC Erlang library. It is designed to make it easy to write XML-RPC Erlang clients and/or servers. The library is compliant with the XML-RPC specification published by http://www.xmlrpc.org/.


call(Socket, URI, Payload)
call(Host, Port, URI, Payload)
call(Socket, URI, Payload, KeepAlive, Timeout)
call(Host, Port, URI, Payload, KeepAlive, Timeout) -> Result
Socket = socket()
URI = string()
Payload = {call, Method, [Value]}
Method = atom()
Value = integer() | float() | string() | Boolean | ISO8601Date | Base64 | Struct | Array
Boolean = true | false
ISO8601Date = {date, string()}
Base64 = {base64, string()}
Struct = {struct, [{Key, Value}]}
Key = atom()
Array = {array, [Value]}
Host = string() | ip()
Port = integer()
KeepAlive = true | false
Timeout = integer()
ResponsePayload = {response, [Value]} | {response, Fault}
Fault = {fault, FaultCode, FaultString}
FaultCode = integer()
FaultString = string()
Result = {ok, ResponsePayload} | {error, Reason} | {ok, Socket, ResponsePayload} | {error, Socket, Reason}
Reason = term()

Calls an XML-RPC server listening on Host:Port. The URI and Payload is used in the HTTP POST request being sent to the server. The Value is converted to XML (see DATA TYPES below) and is used as request body.

If KeepAlive is true a Socket is returned. The socket can be used to send several calls on the same connection in accordance with HTTP 1.1. If no server response is received within Timeout milli-seconds {error, timeout} or {error, Socket, timeout} is returned.

KeepAlive and Timeout default to false and 60000 milli-seconds.

See EXAMPLES section below.

start_link(Port, MaxSessions, Timeout, Handler, State)
start_link(IP, Port, MaxSessions, Timeout, Handler, State) -> Result

Handler = {Module, Function}
Module = Function = atom()
Port = MaxSessions = integer()
Timeout = integer()
State = term()
IP = ip()
Result = {ok, Pid} | {error, Reason}
Pid = pid()
Reason = term()

Starts an XML-RPC server listening on IP:Port. If no IP address is given the server listens on Port for all available IP addresses. MaxSessions is used to restrict the number of concurrent connections. If MaxSessions is reached the server accepts no new connections for 5 seconds, i.e. blocking new connect attempts.

Handler is a callback, implemented by Module:Function/2, which is used to instantiate an XML-RPC server. The Timeout value is used if the handler is keepalive oriented. State is the initial state given to Module:Function/2. The resulting Pid can be used as input to xmlrpc:stop/1.

See Module:Function/2 and EXAMPLES below.

stop(Pid) -> Result

Pid = pid()
Result = void()

Stops a running XML-RPC server.

Module:Function(State, Payload) -> Result

State = term()
Payload = <See above>
Result = {KeepAlive, ResponsePayload} | {KeepAlive, State, Timeout, ResponsePayload}
KeepAlive = true | false
ResponsePayload = <See above>
Timeout = integer()

It is up to you to implement Function clauses in Module to instantiate an XML-RPC server. Every time an XML-RPC call arrives the Value in the Payload gets converted to Erlang format and is passed on to Module:Function/2.

A Function clause is supposed to return either a 2-tuple or a 4-tuple. KeepAlive must be false in a 2-tuple and true in a 4-tuple. KeepAlive decides if the connection to the client should be kept open or not, i.e. compare with the KeepAlive argument to call/{3,4,5,6} above.

State can be used as a state variable by the callback function and changes made to it is propagated to the next call to Module:Function/2. The state variable is only meaningful if both the client and the server is keepalive oriented. The Timeout specified in start_link/{1,5,6} can be updated in the returning 4-tuple.

If KeepAlive is true and no call arrives within Timeout milli-seconds the socket is closed. The socket may be closed by the client before the specified timeout.

See EXAMPLES below.


The conversion of Value in Payload and ResponsePayload (see above) is done as follows:

XML-RPC data type       Erlang data type
-----------------       ----------------
<int>                   integer()
<boolean>               true or false
<string>                string()
<double>                float()
<dateTime.iso8601>      {date, string()}
<struct>                {struct, [{Key, Value}]}
<array>                 {array, [Value]}
<base64>                {base64, string()}

Read more about the XML-RPC data types in the XML-RPC specification published by http://www.xmlrpc.org/.

Here are some examples on how Erlang format is converted to XML:

"Kilroy was here"
<string>Kilroy was here</string>
{date, "19980717T14:08:55"}
{struct, [{foo, 42}, {bar, 4711}]}
{array, [42, 42.5}
{date, "19980717T14:08:55"}


You are strongly advised to inspect the example code in the examples/ directory.

The first example (fib_server.erl) calculates Fibonacci values and is a non-keepalive server. The second example (echo_server.erl) echoes back any incoming parameters and is a non-keepalive server. The third example (date_server.erl) calculates calendar values for given dates and is a keepalive server which uses the state variable to provide login state and different timeout settings. The fourth example (validator.erl) is a validation server which can be used to validate the library using the http://validator.xmlrpc.org/ service.

A snippet from the Fibonacci callback module in the examples/ directory:

handler(_State, {call, fib, [N]}) when integer(N) ->
    {false, {response, [fib(N)]}};
handler(_State, Payload) ->
    FaultString = lists:flatten(io_lib:format("Unknown call: ~p", [Payload])),
    {false, {response, {fault, -1, FaultString}}}.

fib(0) -> 1;
fib(1) -> 1;
fib(N) -> fib(N-1)+fib(N-2).

and how it can be called:

1> xmlrpc:call({127, 0, 0, 1}, 4567, "/", {call, fib, [0]}). 
2> xmlrpc:call({127, 0, 0, 1}, 4567, "/", {call, fib, [4]}).

Again: You are strongly advised to inspect the example code in the examples/ directory.


Home for the XML-RPC specification.
Main README file for the library.
Example code


Joakim Grebeno - jocke [at] gleipnir.com