I'm using STM32 with ESp8266 using latest AT Command Firmware V2
Also i'm including https://github.com/nimaltd/ESP8266
Which helps parse at commands
I can connect to my router access point and my local tcp server but when sending GET requests i receive nothing on my local
const char* host = "192.168.1.9";
while(!Wifi_TcpIp_StartTcpConnection(0,host,3437,10)){
char buffer[] = "Unable to connect to TCP Backend\r\n";
HAL_UART_Transmit(&huart1,buffer,sizeof(buffer),HAL_MAX_DELAY);
};
uint8_t req ="GET /opaaa HTTP/1.1\r\n"; Wifi_TcpIp_SendDataTcp(0,sizeof(req),&req); //success but i receive nothing
Assuming the TCP communication works properly (you can connect to the server, send and receive data) and that the host you connect to serves HTTP on that port, the issue I can see with your request is that you're missing an additional CRLF at the end, like so:
char *req = "GET /opaaa HTTP/1.1\r\n\r\n";
Wifi_TcpIp_SendDataTcp(0, strlen(req), (uint8_t*)req);
This signifies the end of HTTP headers that you're sending. In your original case, the server may still be waiting for more headers and therefore holding with sending the response back to you.
I also suggest to clean up the sending code, one way of which I've pasted above - you were assigning a string to a single byte uint8_t variable.
Related
I have the Telit LE920-EUG 4G LTE module. I am trying to execute GET and POST http requests to a remote server. Though the PDP context is activating properly and I have internet access on the SIM that I'm using, I can't seem to be able to connect to a remote server and execute HTTP requests (both POST and GET) from the module.
I have tried two ways, one through direct HTTP commands supported by the module(All commands mentioned in the LE9x0 AT command reference guide), the commands sequence for which is mentioned below, but +CME ERROR: 100 occurs, and it's same for every http command(AT#HHTPQRY, AT#HTTPRCV) that I try to execute.
AT#SGACT=1,1
#SGACT: 31.81.208.1
OK
AT#HTTPCFG=0,"httpbin.org",80,0,,,0,120,1
+CME ERROR: 100
//No configuration details
AT#HTTPCFG?
+CME ERROR: 100
AT#HTTPCFG=?
+CME ERROR: 100
I have also tried the GET and POST commands after socket dialing. The socket connects but they are not receiving any data from the server or posting anything onto the server, the connection closes with a NO CARRIER. The command sequence that I'm using is given below
//Socket Dial
AT#SD=1,0,80,www.m2msupport.net
CONNECT
//GET commands sequence
GET /m2msupport/http_get_test.php HTTP/1.1
Host:www.m2msupport.net
Connection:keep-alive
//Connection closes with No Response
NO CARRIER
//Socket info shows the bytes sent
at#si=1
#SI: 1,86,0,0,0
OK
I am developing an application in which i am using socket for the communication between server application and client application(web and desktop both). My server application continuously listening the request of the client application and accept the request whenever comes.
Server code :
TcpListener listener = new TcpListener(IPAddress.Parse(ipAddStr), portNum);
listener.Start();
while (listen)
{
TcpClient handler = listener.AcceptTcpClient();
// doing some stuff
// for every client handler i am creating a new thread and start listening for the next request
}
and for web client i am using WebSocket, as for establishing the connection with WebSocket client we have to follow some handshaking process. and for that I am using the following code (which is working fine) :
static private string guid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
private static string AcceptKey(ref string key)
{
string longKey = key + guid;
SHA1 sha1 = SHA1CryptoServiceProvider.Create();
byte[] hashBytes = sha1.ComputeHash(System.Text.Encoding.ASCII.GetBytes(longKey));
return Convert.ToBase64String(hashBytes);
}
generating and sending response for handshaking with websocket client:
// generate accept key fromm client header request
var key = headerRequest.Replace("ey:", "`")
.Split('`')[1]
.Replace("\r", "").Split('\n')[0]
.Trim();
var responseKey = AcceptKey(ref key);
//create the response for the webclient
var newLine = "\r\n";
var response = "HTTP/1.1 101 Switching Protocols" + newLine
+ "Upgrade: websocket" + newLine
+ "Connection: Upgrade" + newLine
+ "Sec-WebSocket-Accept: " + responseKey + newLine + newLine;
//send respose to the webclient
Byte[] sendBytes = Encoding.ASCII.GetBytes(response);
networkStream.Write(sendBytes, 0, sendBytes.Length);
networkStream.Flush();
I have also TcpClient socket used for desktop application, so the problem is how to identify that the request is from WebSocket or from TcpClient ?
The easiest way would be to have a websocket listener and the vanilla TCP listener listen to different port numbers. You should do that anyway, because it is customary for websocket applications to run on the standard http port 80 (or standard https port 443 when you use websockets with TLS), while a custom protocol based on TCP should run on one of the ports from the "registered" range between 1024 to 49151. You are well-advised to follow this, because a well-secured client environment which allows web access but not much else might not allow the user to connect to other ports than 80 and 443, while any non-http traffic on these ports might trigger an intrusion detection system.
When you still want to handle both protocols on the same port for some reason, it will be a bit difficult. Websocket is a protocol based on TCP which looks like a vanilla HTTP GET request at first, until you receive the headers Connection: Upgrade and Upgrade: websocket.
That means connection requests for either protocol need to be accepted by the same listener at first. Only after the client sent enough data to identify its connection attempt as either your custom protocol or websocket (or something completely different which accidentally connected to your port - you will encounter that a lot when you deploy your application facing the internet) and then delegate the communication with the client to the appropriate handler class.
A TcpClient is a Socket wrapper.
WebSocket is a protocol that can run over a TcpClient. WebSocket protocol defines the handshake and how to frame data.
The best way of differentiate simple TCP connections and WebSocket connections is to have them listening in different ports, since you are going to use different protocols. It would be bad if you have them in the same port, it will become a mess.
I'm making a server and client in Python 3.3 using the socket module. My server code is working fine, but this client code is returning an error. Here's the code:
import socket
import sys
import os
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_address = ('192.168.1.5', 4242)
sock.bind(server_address)
while True:
command = sock.recv(1024)
try:
os.system(command)
sock.send("yes")
except:
sock.send("no")
And here's the error:
Error in line: command = sock.recv(1024)
OSError: [WinError 10057] A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied
What on earth is going on?
It looks like you're confused about when you actually connect to the server, so just remember that you always bind to a local port first. Therefore, this line:
server_address = ('192.168.1.5', 4242)
Should actually read:
server_address = ('', 4242)
Then, before your infinite loop, put in the following line of code:
sock.connect(('192.168.1.5', 4242))
And you should be good to go. Good luck!
EDIT: I suppose I should be more careful with the term "always." In this case, you want to bind to a local socket first.
You didn't accept any requests, and you can only recv and/or send on the accepted socket in order to communicate with client.
Does your server only need one client to be connected? If so, try this solution:
Try adding the following before the while loop
sock.listen(1) # 1 Pending connections at most
client=sock.accept() # Accept a connection request
In the while loop, you need to change all sock to client because server socket cannot
be either written or read (all it does is listening at 192.168.1.5:4242).
client:
socket(), connect() and then
for (1 to 1024) {
write(1024 bytes)
}
exit(0);
server:
socket(), bind(), listen()
while (1) {
accept()
while((n = read()) {
if (n == -1) abort(); /* never happended */
total_read += n
}
close()
}
now, client runs on Mac under NAT and server runs on my VPS (abroad)
generally, it works fine (client send all data and exit & server recv all data)
however, when client is running but suddenly the network is broken for couple minutes(and regain), the client won't exit after a long long time... I kill it with control + C and run it again, the server seems not read the data any more (client is still running)
here is what netstat shows:
client:
tcp4 0 130312 192.168.1.254.58573 A.B.C.D.8888 ESTABLISHED
server:
tcp 0 0 A.B.C.D:8888 a.b.c.d:54566 ESTABLISHED 10970/a.out
tcp 102136 0 A.B.C.D:8888 a.b.c.d:60916 ESTABLISHED -
A.B.C.D is my VPS address
a.b.c.d is my public client address
my quesiton is:
1, why ?
2, server will works fine after restarting, how to write code to get rid of it without restarting ?
In TCP, there's no way to tell that a connection has failed unless you try to send something on the connection. TCP doesn't perform active monitoring of the connection (actually, there are optional "keepalive" packets, but these are not normally sent until the connection has been idle for a couple of hours). When you send something, you'll eventually get an error if there's a timeout waiting for the other machine to return an acknowledgement. But if you're just reading data without sending, you can't tell that the connection has failed -- it just looks like the sender doesn't have anything to send.
You can resolve this by designing your application so that the client is required to send something every N seconds. Then set a timer in the server that detects that you haven't received anything for more than N seconds (you should add a little extra time to allow for transient delays).
When the network is broken what happens is that you clients keep sending data and at some point the socket send buffer gets full (I understand from what you show that you are sending 1024 Bytes, 1024 times, 1MB in total). The default for send buffer could be 16KB (surely less than 1MB). Then when the client tries to write, it gets blocked forever.
BTW, now I'm answering your question I don't know whether eventually after a number of TCP timeouts, TCP gives up and closes the socket making the socket interface return with error. I think that's not happening ... :) - So, connect fails if there is a problem in the network but write and read do not fail.
In the server side, the server gets blocked in read because it never receives the EOF.
Solution:
In the client side use non-blocking sockets, if the network is broken, at some point write will return with error EWOULDBLOCK. Then you will realize the send buffer is full for some reason. At that point, you could clouse the connection and try to connect again. If the network is broken, you will receive an error.
In the server side also use non-blocking sockets and select() function with a timeout. After a few timeouts you may decide there is a problem with the new connection and close it.
I have a simple Python server which can handle multiple clients:
import select
import socket
import sys
host = ''
port = 50000
backlog = 5
size = 1024
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind((host,port))
server.listen(backlog)
input = [server,sys.stdin]
running = 1
while running:
inputready,outputready,exceptready = select.select(input,[],[])
for s in inputready:
if s == server:
# handle the server socket
client, address = server.accept()
input.append(client)
elif s == sys.stdin:
# handle standard input
junk = sys.stdin.readline()
running = 0
else:
# handle all other sockets
data = s.recv(size)
if data:
s.send(data)
else:
s.close()
input.remove(s)
server.close()
One client connects to it and they can communicate. I have a third box from where I am sending a RST signal to the server (using Scapy). The TCP state diagram does not say if an endpoint is supposed to try to recover a connection when it sees a RESET. Is there any way I can force the server to recover the connection? (I want it to send back a SYN so that it gets connected to the third client)
Your question doesn't make much sense. TCP just doesn't work like that.
Re "The TCP state diagram does not say if an endpoint is supposed to try to recover a connection when it sees a RESET": RFC 793 #3.4 explicitly says "If the receiver was in any other state [than LISTEN or SYN-RECEIVED], it aborts the connection and advises the user and goes to the CLOSED state.".
An RST won't disturb a connection unless it arrives over that connection. I guess you could plausibly forge one, but you would have to know the current TCP sequence number, and you can't get that from within either of the peers, let alone a third host.
If you succeeded somehow, the connection would then be dead, finished, kaput. Can't see the point of that either.
I can't attach any meaning to your requirement for the server to send a SYN to the third host, in response to an RST from the third host, that has been made to appear as though it came from the second host. TCP just doesn't work anything like this either.
If you want the server to connect to the third host it will just have to call connect() like everybody else. In which case it becomes a client, of course.