AFNetworking/AFJSONRPCClient

AFJSONRPCClient *client = [AFJSONRPCClient clientWithEndpointURL:[NSURL URLWithString:@"http://path.to/json-rpc/service/"]];

// Invocation
[client invokeMethod:@"method.name"
    success:^(AFHTTPRequestOperation *operation, id responseObject)
{
    // ...
}   failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    // ...
}];

// Invocation with Parameters
[client invokeMethod:@"method.name"
          parameters:@{@"foo" : @"bar", @"baz" : @(13)}
    success:^(AFHTTPRequestOperation *operation, id responseObject) {
    // ...
}   failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    // ...
}];

// Invocation with Parameters and Request ID
[client invokeMethod:@"method.name"
          parameters:@[@(YES), @(42)]
           requestId:@(2)
    success:^(AFHTTPRequestOperation *operation, id responseObject) {
    // ...
}   failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    // ...
}];

@protocol ArithemeticProtocol
- (void)sum:(NSArray *)numbers
    success:(void (^)(NSNumber *sum))success;
    failure:(void (^)(NSError *error))failure;
@end

AFJSONRPCClient *client = [AFJSONRPCClient clientWithEndpointURL:[NSURL URLWithString:@"http://path.to/json-rpc/service/"]];

[[client proxyForProtocol:@protocol(ArithemeticProtocol)] sum:@[@(1), @(2)]
    success:^(NSNumber *sum) {
    // ...
}   failure:^(NSError *error) {
    // ...
}];

MyJSONRPCClient *client = [MyJSONRPCClient sharedClient];

[client sum:@[@(1), @(2)]
    success:^(NSNumber *sum) {
    // ...
}   failure:^(NSError *error) {
    // ...
}];

platform :ios, '5.0'

pod 'AFJSONRPCClient', '0.1.0'