Add timeouts to GSMClient

[dzindra]

Timeouts on connect and write prevents sketch lockups due to poorly powered modem.

[Rocketct]

Tested by setting, in example GSMWebClient:

• client.setSocketTimeout(1); and client.setConnectTimeout(1); timeout reached and request not done;
• client.setSocketTimeout(10000); and client.setConnectTimeout(10000); timeout not reached and request done and showed on the serial monitor;
• client.setSocketTimeout(100); and client.setConnectTimeout(100); timeout reached and request not done.

The PR works, after the previous tests i have also introduced a little delay higher then the timeout, after the start = millis() where used in the APIs , to force it and also in this case the changes had works;
The sketch used for the test is the following:

/*
  Web client

 This sketch connects to a website through a MKR GSM 1400 board. Specifically,
 this example downloads the URL "http://www.example.org/" and
 prints it to the Serial monitor.

 Circuit:
 * MKR GSM 1400 board
 * Antenna
 * SIM card with a data plan

 created 8 Mar 2012
 by Tom Igoe
*/

// libraries
#include <MKRGSM.h>

#include "arduino_secrets.h" 
// Please enter your sensitive data in the Secret tab or arduino_secrets.h
// PIN Number
const char PINNUMBER[]     = SECRET_PINNUMBER;
// APN data
const char GPRS_APN[]      = SECRET_GPRS_APN;
const char GPRS_LOGIN[]    = SECRET_GPRS_LOGIN;
const char GPRS_PASSWORD[] = SECRET_GPRS_PASSWORD;

// initialize the library instance
GSMClient client;
GPRS gprs;
GSM gsmAccess(true);

// URL, path and port (for example: example.org)
char server[] = "example.org";
char path[] = "/";
int port = 80; // port 80 is the default for HTTP

void setup() {
  // initialize serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }
  client.setSocketTimeout(100);
  client.setConnectTimeout(100);
  Serial.println("Starting Arduino web client.");
  // connection state
  bool connected = false;

  // After starting the modem with GSM.begin()
  // attach the shield to the GPRS network with the APN, login and password
  while (!connected) {
    if ((gsmAccess.begin(PINNUMBER) == GSM_READY) &&
        (gprs.attachGPRS(GPRS_APN, GPRS_LOGIN, GPRS_PASSWORD) == GPRS_READY)) {
      connected = true;
    } else {
      Serial.println("Not connected");
      delay(1000);
    }
  }

  Serial.println("connecting...");
  // if you get a connection, report back via serial:
  if (client.connect(server, port)) {
    Serial.println("connected");
    // Make a HTTP request:
    client.print("GET ");
    client.print(path);
    client.println(" HTTP/1.1");
    client.print("Host: ");
    client.println(server);
    client.println("Connection: close");
    client.println();
  } else {
    // if you didn't get a connection to the server:
    Serial.println("connection failed");
  }
}

void loop() {
  // if there are incoming bytes available
  // from the server, read them and print them:
  if (client.available()) {
    char c = client.read();
    Serial.print(c);
  }

  // if the server's disconnected, stop the client:
  if (!client.available() && !client.connected()) {
    Serial.println();
    Serial.println("disconnecting.");
    client.stop();

    // do nothing forevermore:
    for (;;)
      ;
  }
}

[sandeepmistry]

@cmaglie @facchinm any thoughts on this one?

EthernetClient now has a setConnectionTimeout(timeout) API, should we port to other libraries?

https://github.com/arduino-libraries/Ethernet/blob/7b5ee58ba50ae28341111e4641d35076080b8597/src/Ethernet.h#L241

[facchinm]

I think we could adopt setConnectionTimeout() API broadly, maybe even adding it as a (non pure virtual) function to Client base class

[dzindra]

Any progress with this PR? Should I change function name to setConnectionTimeout() to make sure it is compatible with EthernetClient?

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