How to send all data at once

[joyanhui]

When I send 1540 bytes of data to the TCP server.
The data is split into two packets with a byte count of 1440+100, respectively
And when I send using telnet（pc）or python3-socket（pc）, I can send 1540 bytes at once

import usocket  


def TcpShort(addrFull, payload, timeout) -> str:
    protocolType = addrFull.split("://")[0]
    if protocolType != 'tcp' and protocolType != 'tcpShort':
        print("not support "+protocolType)
        return ""
    try:
        addrFull = addrFull.replace(protocolType+"://", "")
        hostAndport = addrFull.split("/")[0]
        host = hostAndport.split(":")[0]
        port = 80
        if len(hostAndport.split(":")) > 1:
            port = hostAndport.split(":")[1]        
        request = payload.encode()
        print("request Len: " + str(len(request)))
        s = usocket.socket(usocket.AF_INET, usocket.SOCK_STREAM)
        addr = usocket.getaddrinfo(host, port)[0][-1]
        s.connect(addr)
        #s.send(request)  
        tmpLen=s.write(request)  
        print("tmpLen: " + str(tmpLen))
        response = b""  # 
        s.settimeout(timeout)  # 
        while True:
            try:
                data = s.recv(4096)
                if not data:
                    break
                response += data
                if b'\n' in data:
                    break
            except OSError:
                break
        try:
            s.close()
        except Exception as e2:
            print("TcpShort socket close err 1 ", str(e2))
            return ""
        return response.decode()
    except Exception as e:
        print("TcpShort socket err", str(e))
        try:
            s.close
        except Exception as e2:
            print("TcpShort socket close err 2", str(e2))
            return ""
        return ""
    
# test
payloadStr: str = "v1Set!xl:4827e25702c4!16!0a484b5c79ddb3c933c67a97194501a1!760532712!Sr5sLSyfjqUR8LBp0DHM6HfnYDLR09vmxwLNlM_fn7fa6Psm-4vWjEvooi6OsT5b8a_k7w-wOuGB2PHPUPMse2zj9YxYOyEDQejFDf_ESqe3ESDa_evh8rnZWF7j3jsYjB-BsCF1jWS41M2UI7UjDX_3QZGZ9EScMmMOZykAkWN8AJUbjsEbc_gofOmxjAabmSvKcHh1zhK3IQcomP3s5oBj2T32oV098jR3IqZsPkaAOcvr-LHSETaTmwKmjd-Qb00haPiuuTWxVqm0gPJ3nz-JzWTh8_9H8Jv9IMWbH0mh2T-KuzcHFGevPGqNM-5GdGo4iISCkx10Sekj1TDb1YHyS6G1A6MZCWHcjml5iQ0Ull-Wynp1EOqZHInbOl0h4JDEyFEk4UAGGr705_FwB_6R6WRJd1Ma6UFfP2HtbU0BsMoHLcTlhdsuURRdHY33KAJCD4pdduuGKeCqtRVLFa4furAjbsqnvivg44FIVyxDmxFSKf9SkgMJ3OiwpVn9bWTiuKlJu1ezb5L68JkNGcOEf94hC34XKCBI6uTA0pKZg6bTAru5ZknCa3-PeSmJAP7mznL3lLPinMIEhuoF0y09qGTVIIleM9wCsmZHa5Gdw8YndeVzlHKA9BBO5GMMuUFMBH4bbCj0onuiJ7vlYxO7PMQF-pEIk0TcZyjL__XqhAA07xg-L-xF4tfvHI-MBgJNrfjCPayIfYsjxtQ23V5uXhfoAeluzZNxPjr3f857VPxagTU4VgAUlZYC7qH0LqoKHsngAnEV38QIOFC4H3T3KOykT-Vf-z8xbZQ2u-0h2GAb4h1blmg9li9zmRXhoE88q9_H8PUP3d1CklPtP6Mqi0b2f3GPM9YqSAvEF-IfZ4nepn9dRmKg18Wnz8IC0_7gaOXX_C-OcSuR60Qk9WwRw0pyjig75VwY6ZFQ0MyuGM_1T8nIeIt84Ks272LWFHpIPt7s9uFcM0AtGbeg_SK4NkjRg6F1DrXKLqtFXZfszK19_WWvG2bEpsByvmjcuu_4Sye6OxBgpkyS1yxMsBQKCwoa4kaPtdXCxFHBLT6wLw4uS11Ym_Z5d36X035j6v5W9l9dst5hzsnUq1C2ZOLAuptiKkRTt-O-jzZTPGaJc-K79xtT8dyUn0CuRylRCbl1XFCSu2ZgEeebpJ8s-zEiNA3wZq9ZsEMQsNmD_433XUY4FAdQTFRAD-iQvFcUuKb2yhJ4zu1diw_pIstvrOZy04CNdxLtKswNYFN3CaiGVU-egu_r-Ao-SIUXgFi-G7ARsnNBpUKeL3NXjcStEa_b-ldZrzSZc2fTca_kH7CykR47q-x-pAVj9CxCMMZK10i1rCeHyMWqfWRFmKmztb9kW8xI0x7aUZwLosHs52ljg8dvwHyZQGEU2rYNehGvbvaz1M-Y1qaRZIym9w9M-qlmQc7ymnIjr3TKBDpq8UcoNT6wQj12l5TdcrtmzOWX"
print("payloadStr Len: " + str(len(payloadStr)))
req=TcpShort("tcp://10.1.1.6:18007", payloadStr, 5)
print(req)

[Josverl]

What version, port and what nic are you using?

[joyanhui]

Thank you for your reply.
It seems to be caused by IWIP and tcp mss, but I don't know how to solve it.

esp32 LOLIN_S2_MINI
esp-idf-v5.0.4
micropython-1.22.1

[jimmo]

I'm pretty sure this is the expected behavior. The MSS on esp32 is 1440 (see components/lwip/Kconfig). It's below the MTU so you won't see IP fragmentation.

The tests you're doing from your PC, are they actually going over a network (or is it the same host).

[joyanhui]

Thank you for your answer. Is there a way to avoid this situation?

I tried running this script using Python 3 on a PC (10.1.1.133) and it was possible to send complete data to the TCP server (10.1.1.6). However, ESP32 (10.1.1.150) is still divided into two packages.

#import usocket  esp32 
import socket as usocket #  pc 

def Tcp(host,port, payload, timeout) -> str:
    request = payload.encode()
    print("request Len: " + str(len(request)))
    s = usocket.socket(usocket.AF_INET, usocket.SOCK_STREAM)
    addr = usocket.getaddrinfo(host, port)[0][-1]
    s.connect(addr)
    tmpLen=s.send(request)  
    #tmpLen=s.write(request)  
    print("tmpLen: " + str(tmpLen))
    response = b""  # 
    s.settimeout(timeout)  
    while True:
            try:
                data = s.recv(4096)
                if not data:
                    break
                response += data
                if b'\n' in data:
                    break
            except OSError:
                break
    return response.decode()


# test
payloadStr: str = "v1Set!xl:4827e25702c4!16!0a484b5c79ddb3c933c67a97194501a1!760532712!Sr5sLSyfjqUR8LBp0DHM6HfnYDLR09vmxwLNlM_fn7fa6Psm-4vWjEvooi6OsT5b8a_k7w-wOuGB2PHPUPMse2zj9YxYOyEDQejFDf_ESqe3ESDa_evh8rnZWF7j3jsYjB-BsCF1jWS41M2UI7UjDX_3QZGZ9EScMmMOZykAkWN8AJUbjsEbc_gofOmxjAabmSvKcHh1zhK3IQcomP3s5oBj2T32oV098jR3IqZsPkaAOcvr-LHSETaTmwKmjd-Qb00haPiuuTWxVqm0gPJ3nz-JzWTh8_9H8Jv9IMWbH0mh2T-KuzcHFGevPGqNM-5GdGo4iISCkx10Sekj1TDb1YHyS6G1A6MZCWHcjml5iQ0Ull-Wynp1EOqZHInbOl0h4JDEyFEk4UAGGr705_FwB_6R6WRJd1Ma6UFfP2HtbU0BsMoHLcTlhdsuURRdHY33KAJCD4pdduuGKeCqtRVLFa4furAjbsqnvivg44FIVyxDmxFSKf9SkgMJ3OiwpVn9bWTiuKlJu1ezb5L68JkNGcOEf94hC34XKCBI6uTA0pKZg6bTAru5ZknCa3-PeSmJAP7mznL3lLPinMIEhuoF0y09qGTVIIleM9wCsmZHa5Gdw8YndeVzlHKA9BBO5GMMuUFMBH4bbCj0onuiJ7vlYxO7PMQF-pEIk0TcZyjL__XqhAA07xg-L-xF4tfvHI-MBgJNrfjCPayIfYsjxtQ23V5uXhfoAeluzZNxPjr3f857VPxagTU4VgAUlZYC7qH0LqoKHsngAnEV38QIOFC4H3T3KOykT-Vf-z8xbZQ2u-0h2GAb4h1blmg9li9zmRXhoE88q9_H8PUP3d1CklPtP6Mqi0b2f3GPM9YqSAvEF-IfZ4nepn9dRmKg18Wnz8IC0_7gaOXX_C-OcSuR60Qk9WwRw0pyjig75VwY6ZFQ0MyuGM_1T8nIeIt84Ks272LWFHpIPt7s9uFcM0AtGbeg_SK4NkjRg6F1DrXKLqtFXZfszK19_WWvG2bEpsByvmjcuu_4Sye6OxBgpkyS1yxMsBQKCwoa4kaPtdXCxFHBLT6wLw4uS11Ym_Z5d36X035j6v5W9l9dst5hzsnUq1C2ZOLAuptiKkRTt-O-jzZTPGaJc-K79xtT8dyUn0CuRylRCbl1XFCSu2ZgEeebpJ8s-zEiNA3wZq9ZsEMQsNmD_433XUY4FAdQTFRAD-iQvFcUuKb2yhJ4zu1diw_pIstvrOZy04CNdxLtKswNYFN3CaiGVU-egu_r-Ao-SIUXgFi-G7ARsnNBpUKeL3NXjcStEa_b-ldZrzSZc2fTca_kH7CykR47q-x-pAVj9CxCMMZK10i1rCeHyMWqfWRFmKmztb9kW8xI0x7aUZwLosHs52ljg8dvwHyZQGEU2rYNehGvbvaz1M-Y1qaRZIym9w9M-qlmQc7ymnIjr3TKBDpq8UcoNT6wQj12l5TdcrtmzOWX"

print("payloadStr Len: " + str(len(payloadStr)))
req=Tcp("10.1.1.6",18007, payloadStr, 5)
print(req)