# Set UDPSocket reciever buffer size?

**URL:** <https://discourse.julialang.org/t/set-udpsocket-reciever-buffer-size/3939>\
**Category:** General Usage\
**Tags:** networking\
**Created:** [May 26, 2017, 4:04pm UTC](https://discourse.julialang.org/t/set-udpsocket-reciever-buffer-size/3939 "2017-05-26T16:04:53Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![ggggggggg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ggggggggg/32/265_2.png) [@ggggggggg](https://discourse.julialang.org/u/ggggggggg)\
**Post date:** [May 26, 2017, 4:04pm UTC](https://discourse.julialang.org/t/set-udpsocket-reciever-buffer-size/3939/1 "2017-05-26T16:04:53Z")

</div>

I would like to increase the recieve buffer size of a UDP socket, but I don’t see how to do it. In C++ I would do

```
setsockopt(sd, SOL_SOCKET, SO_RCVBUF, &sockbufsize, (socklen_t)sizeof(sockbufsize));

```

But the closest function I can find is `setopt` which doesn’t seem to support this. Any ideas?

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<div class="post-metadata">

**Author:** ![ggggggggg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ggggggggg/32/265_2.png) [@ggggggggg](https://discourse.julialang.org/u/ggggggggg)\
**Post date:** [May 26, 2017, 4:56pm UTC](https://discourse.julialang.org/t/set-udpsocket-reciever-buffer-size/3939/2 "2017-05-26T16:56:32Z")

</div>

It looks like maybe I want to call `int uv_recv_buffer_size(uv_handle_t* handle, int* value)`. The libuv docs say "Gets or sets the size of the receive buffer that the operating system uses for the socket. If \*value == 0, it will return the current receive buffer size, otherwise it will use \*value to set the new receive buffer size. This function works for TCP, pipe and UDP handles on Unix and for TCP and UDP handles on Windows.

So I tried

```
 udpsock = UDPSocket()
 err = ccall(:uv_recv_buffer_size, Cint, (Ptr{Void}, Ptr{Cint}), udpsock.handle, Cint[0])

```

But I’m getting `err=-9` which suggests I’m probably doing something wrong.

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<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [May 27, 2017, 8:26am UTC](https://discourse.julialang.org/t/set-udpsocket-reciever-buffer-size/3939/3 "2017-05-27T08:26:46Z")

</div>

We also have problems with receiving UDP messages in Julia: Many of them get lost. I am not sure, if the buffersize is the problem, could also be something else.

---

<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [May 27, 2017, 8:31am UTC](https://discourse.julialang.org/t/set-udpsocket-reciever-buffer-size/3939/4 "2017-05-27T08:31:13Z")

</div>

Example code:

```julia
using DataStructures

# disable SIG_INT
println("To termiate the logger, press <CTRL>+<C>!")
ccall(:jl_exit_on_sigint, Void, (Cint,), 0)

# use an array with one element for global variables, such that they can be declared as const
const terminate = [false]

# create a queue for buffering incoming messages
const q = Queue(String)

# background loop for receiving UDP messages, terminated with <ctrl> + <c>
function receiveData(server_ip)
	global terminate
	udpsock = UDPSocket()
	# setopt(udpsock, enable_broadcast=true)
	bind(udpsock, server_ip, port)
	i = 0
	try
		while true
			msg = String(copy(recv(udpsock)))
			enqueue!(q, msg)
		end
	catch my_exception
		if isa(my_exception, InterruptException)
			close(udpsock)
			terminate[1] = true
		end
	end
end

server_ip = IPv4("0.0.0.0")
@async receiveData(server_ip) # start the background task of receiving UDP packages

```

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<div class="post-metadata">

**Author:** ![ggggggggg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ggggggggg/32/265_2.png) [@ggggggggg](https://discourse.julialang.org/u/ggggggggg)\
**Post date:** [May 30, 2017, 4:57pm UTC](https://discourse.julialang.org/t/set-udpsocket-reciever-buffer-size/3939/5 "2017-05-30T16:57:45Z")

</div>

I managed to get `uv_recv_buffer_size` to work with the following:

```julia
  port = 40788
  udpsock = UDPSocket()
  didbind = bind(udpsock,ip"127.0.0.1",port)
  @assert didbind
  arg = Ref{Cint}(0) # pass 0 to read the value
  Base.uv_error("buffer size",ccall(:uv_recv_buffer_size, Cint, (Ptr{Void}, Ptr{Cint}), udpsock.handle, arg))
  @show arg
  arg = Ref{Cint}(100000) # pass nonzero to set the value (doubled on linux)
  Base.uv_error("buffer size",ccall(:uv_recv_buffer_size, Cint, (Ptr{Void}, Ptr{Cint}), udpsock.handle, arg))
  @show arg
  arg = Ref{Cint}(0) # pass 0 to read the value
  Base.uv_error("buffer size",ccall(:uv_recv_buffer_size, Cint, (Ptr{Void}, Ptr{Cint}), udpsock.handle, arg))
  @show arg

```