when Ethernet.begin(mac) recalled to refresh new ip，udp can't work

[pgmsoul]

when udp has send a data once，if recall Ethernet.begin(mac)，then can't send success，error is “previous packet on that connection not sent yet”

[pgmsoul]

    bool initDhcp(){
        if(!dhcp) return true;
        int ret;
        etherUdp.udp.stop();
        unsigned long t = millis();
        ret = Ethernet.begin(mac);
        print_f("get dhcp success:%d\n",millis()-t);
        if(ret){
            cfg.etherIP = Ethernet.localIP();
            Serial.print("localIP: ");
            Serial.println(cfg.etherIP);
            Serial.print("subnetMask: ");
            Serial.println(Ethernet.subnetMask());
            Serial.print("gatewayIP: ");
            Serial.println(Ethernet.gatewayIP());
            Serial.print("dnsServerIP: ");
            Serial.println(Ethernet.dnsServerIP());
            bool b = etherUdp.udp.begin(UDP_MODLE_PORT);
            print_f("udp server startup in port %d %s\n",UDP_MODLE_PORT,b?"success":"failed");
        }else{
            print_f("get dhcp failed");
        }
        dhcp = ret==0;
        return ret!=0;
    }

    int send(const char* data,int len = 0){
        IPAddress servIp = udp.remoteIP();
        Serial.println(servIp);
        //EthernetUDP cudp;
        if(!cudp.beginPacket(servIp,UDP_SERV_PORT)) return 0;
        if(len==0) len = strlen(data);
        len = cudp.write(data,len);
        cudp.endPacket();
        print_f("send complete %d\n",len);
        return len;
    }

void EtherUdp::recv(){
    int size = udp.parsePacket();
    if(size<=0) return;
    char buf[512];//not recv long message ,limit to 128 bytes
    size = udp.read(buf,sizeof buf);
    buf[size] = 0;
    if(strcmp(buf,"get_net_modle_param")==0){
        String str = cfg.infoString();
        send(str.c_str(),str.length());
    }else if(strcmp(buf,"set_net_modle_param")==0){
        if(cfg.parseParam(buf)){
            send("ok",0);
        }else{
            send("set_net_modle_param failed",0);
        }
    }else{
        send("command isn't reconnize",0);
    }
    en.dhcp = true;
    print_f("%s\n",buf);
}

[pgmsoul]

and i find resolution:

EthernetUDP udp;
udp.begin(port);
void loop(){
    int len = udp.recv();
    if(len>0){
          some code
          udp.send();
          udp.flush();
          udp.stop();
          udp.begin(prot);
          //every time you must re call all function ,not like in pc only do once
    }
}

[maddogmaycry]

Thx YOU VEARY MUCH!