diff --git a/src/client/main.cr b/src/client/main.cr
index e975128..abb55ac 100644
--- a/src/client/main.cr
+++ b/src/client/main.cr
@@ -111,7 +111,7 @@ def file_transfer(client : IPC::Client, file : File, file_info : FileStorage::Fi
 	buffer_size = 1_000
 
 	buffer = Bytes.new buffer_size
-	counter = 1
+	counter = 0
 	size = 0
 
 	while (size = file.read(buffer)) > 0
diff --git a/src/common/filestorage.cr b/src/common/filestorage.cr
index b115208..4b81e23 100644
--- a/src/common/filestorage.cr
+++ b/src/common/filestorage.cr
@@ -97,7 +97,7 @@ module FileStorage
 		property mid  : String     # autogenerated
 		property file : FileInfo
 
-		def initialize(@file)
+		def initialize(@file : FileInfo)
 			@mid = UUID.random.to_s
 		end
 	end
@@ -177,7 +177,7 @@ module FileStorage
 
 			@filedigest = file_info.digest
 			@data = Base64.encode bindata
-			@chunk = FileStorage::Chunk.new count, file_info.nb_chunks, @data
+			@chunk = FileStorage::Chunk.new count, file_info.nb_chunks - 1, @data
 			@mid = UUID.random.to_s
 		end
 	end
diff --git a/src/common/utils.cr b/src/common/utils.cr
index 36b4aa7..8a4b4c4 100644
--- a/src/common/utils.cr
+++ b/src/common/utils.cr
@@ -4,7 +4,7 @@ def remove_chunk_from_db(transfer_info : TransferInfo, chunk_number : Int32)
 	Context.db_by_filedigest.update transfer_info.file_info.digest, transfer_info
 end
 
-def write_a_chunk(userid : String, file_info : FileInfo, chunk_number : Int32, data : Bytes)
+def write_a_chunk(userid : String, file_info : FileStorage::FileInfo, chunk_number : Int32, data : Bytes)
 
 	# storage: Context.storage_directory/userid/fileuuid.bin
 	dir = "#{Context.storage_directory}/#{userid}"
diff --git a/src/server/handlers.cr b/src/server/handlers.cr
index 4028514..6fcc981 100644
--- a/src/server/handlers.cr
+++ b/src/server/handlers.cr
@@ -20,22 +20,26 @@ def hdl_transfer(message : FileStorage::Transfer, user : User) : FileStorage::Re
 	# Get the transfer info from the db
 	transfer_info = Context.db_by_filedigest.get message.filedigest
 
-	# TODO: if we don't have the information
 	if transfer_info.nil?
-		# TODO
+		# The user has to send an upload request before sending anything
+		# If not the case, it should be discarded
+		raise "file not recorded"
 	end
 
-	# TODO: verify that the chunk sent was really missing
-	chunk_number = message.chunk.n - 1
-
-	# TODO: verify the digest
+	chunk_number = message.chunk.n
 
 	data = Base64.decode message.data
-	write_a_chunk user.uid.to_s, transfer_info.file_info, chunk_number, data
 
-	# TODO: register the file with dodb, with its tags
+	# TODO: verify that the chunk sent was really missing
+	if transfer_info.chunks.select(chunk_number).size > 0
+		write_a_chunk user.uid.to_s, transfer_info.file_info, chunk_number, data
+	else
+		raise "non existent chunk or already uploaded"
+	end
 
-	remove_chunk_from_db transfer_info, message.chunk.n
+	remove_chunk_from_db transfer_info, chunk_number
+
+	# TODO: verify the digest, if no more chunks
 
 	FileStorage::Response.new mid, "Ok"
 
@@ -44,23 +48,45 @@ rescue e
 	FileStorage::Response.new mid.not_nil!, "Not Ok", "Unexpected error: #{e.message}"
 end
 
-# TODO
 # the client sent an upload request
-def hdl_upload(request : FileStorage::UploadRequest,
-	user : User,
-	event : IPC::Event::Message) : FileStorage::Response
+def hdl_upload(request : FileStorage::UploadRequest, user : User) : FileStorage::Response
+
+	mid = request.mid
+	mid ||= "no message id"
 
 	puts "hdl upload: mid=#{request.mid}"
 	pp! request
 
+	# TODO: verify the rights and quotas of the user
+
+	# First: check if the file already exists
+	transfer_info = Context.db_by_filedigest.get request.file.digest
+	if transfer_info.nil?
+		# In case file informations aren't already registered
+		# which is normal at this point
+		transfer_info = TransferInfo.new user.uid, request.file
+		Context.db << transfer_info
+	else
+		# File information already exists, request may be duplicated
+		# In this case: ignore the upload request
+	end
+
+	# file_info.name
+	# file_info.size
+	# file_info.nb_chunks
+	# file_info.digest
+	# file_info.tags
+
 	FileStorage::Response.new request.mid, "Upload OK"
+rescue e
+	puts "Error handling transfer: #{e.message}"
+	FileStorage::Response.new mid.not_nil!, "Not Ok", "Unexpected error: #{e.message}"
 end
 
 # TODO
 # the client sent a download request
 def hdl_download(request : FileStorage::DownloadRequest,
-	user : User,
-	event : IPC::Event::Message) : FileStorage::Response
+	user : User) : FileStorage::Response
 
 	puts "hdl download: mid=#{request.mid}"
 	pp! request
@@ -82,9 +108,9 @@ def hdl_requests(requests : Array(FileStorage::Request),
 	requests.each do |request|
 		case request
 		when FileStorage::DownloadRequest
-			responses << hdl_download request, user, event
+			responses << hdl_download request, user
 		when FileStorage::UploadRequest
-			responses << hdl_upload request, user, event
+			responses << hdl_upload request, user
 		else
 			raise "request not understood"
 		end
diff --git a/src/server/main-loop.cr b/src/server/main-loop.cr
index 645a5ff..33bd0f9 100644
--- a/src/server/main-loop.cr
+++ b/src/server/main-loop.cr
@@ -62,7 +62,7 @@ Context.service.not_nil!.loop do |event|
 			request = FileStorage::UploadRequest.from_json(
 				String.new event.message.payload
 			)
-			response = hdl_upload request, Context.users_status[userid], event
+			response = hdl_upload request, Context.users_status[userid]
 
 			do_response event, response
 		when .download_request?
@@ -70,7 +70,7 @@ Context.service.not_nil!.loop do |event|
 			request = FileStorage::DownloadRequest.from_json(
 				String.new event.message.payload
 			)
-			response = hdl_download request, Context.users_status[userid], event
+			response = hdl_download request, Context.users_status[userid]
 
 			do_response event, response
 		when .response?
@@ -91,7 +91,7 @@ Context.service.not_nil!.loop do |event|
 			transfer = FileStorage::Transfer.from_json(
 				String.new event.message.payload
 			)
-			response = hdl_transfer transfer, Context.users_status[userid], event
+			response = hdl_transfer transfer, Context.users_status[userid]
 
 			do_response event, response
 		end