TCP connection only sending but not receiving messages

Question

I am currently trying to create a simple TCP Peer2Peer communication between two computers via Swift. On my on computer it works fine, but when I move one instance to another computer, it receives messages on the second PC but is not able to send any messages.

I have disabled my Firewall and tried it with a Hotspot on my phone. When I use my Rust Peer2Peer connector, it totally works in any case.

What am I doing wrong?

Here is my full code

P2P.swift

import Foundation
import SocketSwift


class P2P {
    
    
    var reciever: Reciever?
    var sender: Sender?
    
    init(serverPort: Int, otherIp: String, otherPort: Int, ownIp: String) {
        print("Data: \(ownIp):\(serverPort) -> \(otherIp):\(otherPort)")
        _ = Task {
            sender = Sender(serverPort: serverPort, ownIp: ownIp)
            sender?.acceptClient()
            while(true) {
                do {
                    try sender?.writeStream(message: readLine() ?? "No")
                } catch let error {
                    print("Error while sending Data \(error)")
                }
            }
        }
        self.reciever = Reciever(otherIp: otherIp, otherPort: otherPort)
        
        
        while(true){ //programm 
            
        }
    }
}

Reciever.swift

import Foundation
import SocketSwift

class Reciever { //AKA Client for RECIEVING MESSAGES
    let prefix = "RECIEVER: "
    var client: Socket? = nil //on this channel I will recieve data
    init(otherIp: String, otherPort: Int) {
        
        _ = clientConnectAsync(otherPort: otherPort, otherIp: otherIp)
        
        while(true) {
            do {
                print(try readStreamAsync(size: 10) ?? "Nothing to read")
            } catch let error {
                print(prefix + "Error while reading \(error)")
            }
        }
    }
    
    
    
    
    
    //read whats in the incoming pip and retuns a string. takes the size of how many input it should take
    private func readStreamAsync(size: Int) throws -> String? {

        var buffer = [UInt8](repeating: 0, count: size) // allocate buffer
     
        var result: String = "";
        _ = try client?.read(&buffer, size: size) // throws the data into the buffer var
        var isEmpty: Bool = true
        for i in 0...size-1 {
            if buffer[i] != 0 {
                isEmpty = false
            }else {
                break
            }
            result.append(String(Character(Unicode.Scalar(buffer[i]))))
        }
        buffer.removeAll()
        if isEmpty {
            return nil
        }
        
        
        return result
    }
    
    func clientConnectAsync(otherPort: Int, otherIp: String) -> Bool {
        do { //TODO async retry to connect to other
            client = try Socket(.inet, type: .stream, protocol: .tcp) // create client for sending data

            //try client?.connect(address: SocketAddress(port: Port(otherPort), address: otherIp)) // start trying to connect to p2p other server
            //try to connect to server
            print(prefix + " Tries to connect to other peer")
            try client?.connect(port: Port(otherPort), address: otherIp)
            print(prefix + "Reciever could connect to the other peer. Now able to retrieve MSG")
            return true
        } catch {
            print(prefix + "Client could not connect to other server: \(error)") //print the reason why the connection was not successful
        }
        client?.close() // client did not connect. Close pipe!!
        do {
            Thread.sleep(forTimeInterval: 1)
            //try await Task.sleep(nanoseconds: UInt64(0.5/*SECOND(S)*/ * Double(NSEC_PER_SEC))) //waites for X sec bec otherwise the console would be flooded
        } catch {
            print("Error sleeping \(error)")
        }
        return clientConnectAsync(otherPort: otherPort, otherIp: otherIp) //retry bec no connection could be etablished
    }
    
}

Sender.swift

import Foundation
import SocketSwift

class Sender { //AKA SERVER for SENDING messages (I know its confusing)
    var server: Socket? = nil //on this channel I will accept connections
    var send: Socket?
    
    init(serverPort: Int, ownIp: String) {
        do {
            server = try Socket(.inet, type: .stream, protocol: .tcp) //Initialize Server, this is running all time.
            try server?.set(option: .reuseAddress, true) // set SO_REUSEADDR to 1
            try server?.bind(port: Port(serverPort), address: ownIp) // bind 'ownIpt:serverPort'
            try server?.listen() // allow incoming connections
            print("Server on port \(serverPort)")
            
        } catch {
            print("Server creation failed: \(error)")
            
            return
        }
    }
        
    
    //Send message
    public func writeStream(message: String) throws {
        if send == nil {
            
            return
        }
        let inputSt: [UInt8] = ([UInt8])(message.utf8)
        
        do {
            try send?.write(inputSt)
        } catch let error {
            print("Error while sending message \(error)")
        }
        
        print("Message: \(message) should be printed")
    }
    
    func acceptClient() -> Socket? {
        
        do {
            print("trying to accept Peerconnection")
            
            send = try server?.accept()
            print("PEER connected to this server. Now able to send MSG")
        } catch {
            print("Error fetching connection \(error)")
            return nil
        }
        if send == nil {
            print("Peer failed to connected")
            return nil
        } else {
            
            //print("Someone connected \(String(describing:send.))")
            
            /*if send?.fileDescriptor == 5 {
                print("Du kannst nur empfangen")
                //send = try server?.accept()

            }else {
                print("Du kannst nur senden")
            }
            print("Someone connected \(String(describing: send?.fileDescriptor))")*/
            return send
        }
    }
}