java - Very slow sockets on Android over wifi -


i'm having performance problem consistent speed of tcp socket connection between 2 android tablets talking on wifi on same lan. (just enough real problem), round-trripping small payload (< 1400 bytes) between devices can take many seconds. it's not uncommon take 10+ seconds, , in worst case, i've seen round trip time of 4 minutes. socket not broken - it's typically blocking on read operation @ client or server end, , once round trip completes, next 1 take few milliseconds.

if continuously push data through socket, not see problems, , typically remain fast ( < 100ms) , connected day long. however, when drip feed payloads - 1 every couple of seconds, not each round trip take longer, occasionally, see these silly times of 10 seconds or more. i'm not looking high performance, , 3 seconds not problem.

i understand pauses between payloads, android preserve battery briefly turning off wifi radio, , tcp stack may add small delay give app layer time add bit more data payload. these 2 points explain ~120ms rountrips versus 1-5ms roundtrips when payloads sent continuously. however, i've never heard of tcp hanging onto buffered data 30+ seconds before sending.

this not nagle issue - tcp_no_delay set true, , i've played thread priorities , other tcp tuning flags no avail.

i'm using 2 samsung galaxy tabs running lollipop , marshmallow, though have tried asus, archos, lenovo , huawei devices.

there's nothing fancy going on - writing socket looks this:

try {     clientsocket = new socket(serverip, echo_port);     sockettransport transport = new sockettransport(clientsocket);      while (running) {         // blocking call ;-)         onstatuschange("waiting next message", 0);         string msg = theq.take();          onstatuschange("writing new message", 0);          long timestart = system.currenttimemillis();         transport.write(msg);          onstatuschange("waiting response", 0);         string result = transport.read();          onstatuschange(result, system.currenttimemillis() - timestart);          if (result == null) {             running = false;         }     } }

with actual read & writing happening in simple wrapper class looks this:

package com.problem.sockettester;  import java.io.bufferedinputstream; import java.io.bufferedoutputstream; import java.io.datainputstream; import java.io.dataoutputstream; import java.io.ioexception; import java.net.socket;  /**  * wrap reading , writing sockets.  */ public class sockettransport {      static final int iptos_lowcost = 0x02;     static final int iptos_reliability = 0x04;     static final int iptos_throughput = 0x08;     static final int iptos_lowdelay = 0x10;      private datainputstream reader;     private dataoutputstream writer;      private byte[] readbuffer = new byte[4096];      public sockettransport(socket socket) throws ioexception {          socket.setkeepalive(true);         socket.settcpnodelay(true);         socket.settrafficclass(iptos_lowdelay | iptos_reliability);         socket.setreceivebuffersize(4096);         socket.setsendbuffersize(4096);          reader = new datainputstream(new bufferedinputstream(socket.getinputstream()));         writer = new dataoutputstream(new bufferedoutputstream(socket.getoutputstream()));     }      public string read() throws ioexception {          int messagesize = reader.readint();         int bytesread;         int totalread = 0;         int offset = 0;         boolean moretoread = true;          while (moretoread) {             bytesread = reader.read(readbuffer, offset, messagesize);             totalread += bytesread;              if (totalread == messagesize) {                 moretoread = false;             }              offset += bytesread;         }          return new string(readbuffer, 0, messagesize);     }       public int write(string message) throws ioexception {          writer.writeint(message.length());         writer.writebytes(message);         writer.flush();         return message.length();     } }

for challenge, full source of minimal server , client apps can found on github @ https://github.com/nigeldyson/androidsocketissue

any ideas or appreciated - i'm fast running out of ideas.


Comments

Post a Comment

Popular posts from this blog

python - Operations inside variables -

this question has answer here: evaluating mathematical expression in string 12 answers i want make python script finds maximum possible output using 2 operations. problem says there syntax error @ 2nd last line, in b in there. how can fix it? x = 0 = int(input("1st number:")) c = int(input("2nd number:" )) e = int(input("3rd number:" )) in range(4): if == 0: b = "+" elif == 1: b = "-" elif == 2: b = "/" else: b = "*" j in range(4): if j == 0: d = "+" elif j == 1: d = "-" elif j == 2: d = "/" else: d = "*" k = b c d e print(k) if you're after variables e on single line, couldn...
Read more

Generic Map Parameter java -

i having lot of methods of type: public static list<eduusers> getdetails(class c, map<string, integer> params) { list<eduusers> details = null; session session = hibernateutil.getsessionfactory().opensession(); transaction tx = null; try { tx = session.begintransaction(); criteria cr = session.createcriteria(c); (map.entry<string, integer> entry : params.entryset()) { cr.add(restrictions.eq(entry.getkey(), entry.getvalue())); } details = cr.list(); tx.commit(); } catch (exception asd) { log.debug(asd.getmessage()); if (tx != null) { tx.commit(); } } { session.close(); } return details; } i trying have generic method them , have written far: public static <t> list<t> getdetails(class<t> c, class<t> b) { l...
Read more

arrays - What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it? -

what arrayindexoutofboundsexception mean , how rid of it? here code sample triggers exception: string[] name = {"tom", "dick", "harry"}; for(int = 0; i<=name.length; i++) { system.out.print(name[i] +'\n'); } your first port of call should documentation explains reasonably clearly: thrown indicate array has been accessed illegal index. index either negative or greater or equal size of array. so example: int[] array = new int[5]; int boom = array[10]; // throws exception as how avoid it... um, don't that. careful array indexes. one problem people run thinking arrays 1-indexed, e.g. int[] array = new int[5]; // ... populate array here ... (int index = 1; index <= array.length; index++) { system.out.println(array[index]); } that miss out first element (index 0) , throw exception when index 5. valid indexes here 0-4 inclusive. correct, idiomatic for statement here be: for (int index = 0; index <...
Read more