Are there limits on string length in Arduino? -

i've been trying hours put simple json object string on arduino send raspberry pi running node.

i cannot seem build string. have tried building string in 1 go:

"{" + string1 + "," + string2 + "," + string3 + "}" etc... 

i've tried using string.replace function. each time end bit of string, or none @ all. below code shows what's happening:

string msg = "{ \"message\" : \"statusupdate\", "; string active = " \"active\" : token, "; string intaketemp = " \"intaketemp\" : token, "; string intakehumid = " \"intakehumid\" : token, "; string exhausttemp = " \"exhausttemp\" : token, "; string exhausthumid = " \"exhausthumid\" : token, "; string targethumid = " \"targethumid\" : token, "; string completed = " \"taskcompleted\" : token }";   if(isactive)   active.replace("token","true"); else   active.replace("token","false");  intaketemp.replace("token",floattostring(intaketemperature,0)); intakehumid.replace("token",floattostring(intakehumidity,0)); exhausttemp.replace("token",floattostring(exhausttemperature,0)); exhausthumid.replace("token",floattostring(exhausthumidity,0)); targethumid.replace("token",floattostring(targethumidity,0));  if(taskfinished)   taskcompleted.replace("token","true"); else   taskcompleted.replace("token","false");      string body = msg;   serial.println(body);   body += active;   serial.println(body);   body += intaketemp;   serial.println(body);   body += intakehumid;   serial.println(body);   body += exhausttemp;   serial.println(body);   body += exhausthumid;   serial.println(body);   body += targethumid;   serial.println(body);   body += taskcompleted;   serial.println(body); 

you can see last bit of code above string being built, i'm spitting out serial monitor. however, here serial output:

{ "message" : "statusupdate",  { "message" : "statusupdate",  "active" : false,  { "message" : "statusupdate",  "active" : false,  "intaketemp" : 0.0,  { "message" : "statusupdate",  "active" : false,  "intaketemp" : 0.0,  "intakehumid" : 0.0,  { "message" : "statusupdate",  "active" : false,  "intaketemp" : 0.0,  "intakehumid" : 0.0,  "exhausttemp" : 0.0,  { "message" : "statusupdate",  "active" : false,  "intaketemp" : 0.0,  "intakehumid" : 0.0,  "exhausttemp" : 0.0,  { "message" : "statusupdate",  "active" : false,  "intaketemp" : 0.0,  "intakehumid" : 0.0,  "exhausttemp" : 0.0,  { "message" : "statusupdate",  "active" : false,  "intaketemp" : 0.0,  "intakehumid" : 0.0,  "exhausttemp" : 0.0,  

is there limit string length? haven't found mention of such limits in docs. there's not else sketch except standard ethernet library , code send via http request (from sample project).

any idea might happening?

edit: ok, i've shortened string so:

string msg = "{ \"m\" : \"status\", "; string active = " \"a\" : token, "; string intaketemp = " \"it\" : token, "; string intakehumid = " \"ih\" : token, "; string exhausttemp = " \"et\" : token, "; string exhausthumid = " \"eh\" : token, "; string targethumid = " \"th\" : token, "; string dryerjustfinished = " \"f\" : token }"; 

and sure enough, it's started work:

{ "m" : "status",  { "m" : "status",  "a" : false,  { "m" : "status",  "a" : false,  "it" : 0.0,  { "m" : "status",  "a" : false,  "it" : 0.0,  "ih" : 0.0,  { "m" : "status",  "a" : false,  "it" : 0.0,  "ih" : 0.0,  "et" : 0.0,  { "m" : "status",  "a" : false,  "it" : 0.0,  "ih" : 0.0,  "et" : 0.0,  "eh" : 0.0,  { "m" : "status",  "a" : false,  "it" : 0.0,  "ih" : 0.0,  "et" : 0.0,  "eh" : 0.0,  "th" : 0.0,  { "m" : "status",  "a" : false,  "it" : 0.0,  "ih" : 0.0,  "et" : 0.0,  "eh" : 0.0,  "th" : 0.0,  "f" : false } 

which means there limitation. memory limitation?

by way, hardware arduino uno r3

atmel processor has limited memory management easy end fragmented memory. remember runtime stack , heap limited.

static string can put progmem also

there freememory function on arduino.cc show how free memory have.