Can not read data from server using GCDAsyncSocket

I tried to connect to the server and send some information to the server(like username, password..), and the server send me back the ID (string type). The problem is I can not get the ID. Could anyone help me? I am beginner in IOS coding. Thanks.

Here is the codes:

1. After I click the button, it will call my own function to get serverIP which is a string and Port which is a int.

2. Then that function will call this function to connect the server:

   (void)logInCheck {
   
       asyncSocket = [[GCDAsyncSocket alloc] initWithDelegate:self delegateQueue:dispatch_get_main_queue()];   
       NSError *error = nil;
       uint16_t port = serverPort;
   
       if (![asyncSocket connectToHost:serverIP onPort:port error:&error])
       {
           DDLogError(@"Unable to connect to due to invalid configuration: %@", error);
       }
       else
       {
           DDLogVerbose(@"Connecting...");
           [self passDataToServer];
       }
   }
   
   //DataPassToServer is a NSString that hold my data
   
   (void)passDataToServer
   {
       NSData *requestData = [DataPassToServer dataUsingEncoding:NSUTF8StringEncoding];
       [asyncSocket writeData:requestData withTimeout:-1.0 tag:0];
       [asyncSocket readDataWithTimeout:-1 tag:0];
   }
   
   //this function call successfully
   
   -(void)socket:(GCDAsyncSocket *)sock didConnectToHost:(NSString *)host port:(UInt16)port
   {
       DDLogVerbose(@"socket:didConnectToHost:%@ port:%hu", host, port);
   }
   
   //this function call successfully
   
   (void)socket:(GCDAsyncSocket *)sock didWriteDataWithTag:(long)tag
   {
       DDLogVerbose(@"socket:didWriteDataWithTag:");
   }
   
   //This function does not run !!! Nothing print out. 
   
   (void)socket:(GCDAsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag
   {
       DDLogVerbose(@"socket:didReadData:withTag:");
       NSString *response = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
       NSLog(@"ID = %@",response);
       [asyncSocket readDataWithTimeout:-1 tag:0];
   }
   

I don't know about your server implementation but, most implementations would read up to the first newline character before processing the request.

So make sure that your [DataPassToServer dataUsingEncoding:NSUTF8StringEncoding] includes a newline character ("\n") at the end.

Your code looks fine and works for me.