Histórico

// Pix recebido
{
"pix": [
{
"endToEndId": "E1803615022211340s08793XPJ",
"txid": "fc9a43k6ff384ryP5f41719",
"chave": "2c3c7441-b91e-4982-3c25-6105581e18ae",
"valor": "0.01",
"horario": "2020-12-21T13:40:34.000Z",
"infoPagador": "pagando o pix"
}
]
}

java
public static Cob createCharge(String token, String payload) {
Cob cob = null;
try {
Generex txid = new Generex("[a-zA-Z0-9]{26,35}");
URL url = new URL("https://api-pix-h.gerencianet.com.br/v2/cob/" + txid.random());
HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
conn.setDoOutput(true);
conn.setRequestMethod("PUT");
conn.setRequestProperty("Content-Type", "application/json");
conn.setRequestProperty("Authorization", "Bearer " + token);

OutputStream os = conn.getOutputStream(); // O erro do connection reset ocorre aqui
os.write(payload.getBytes());
os.flush();

int responseCode = conn.getResponseCode();

StringBuilder responseBuilder = new StringBuilder();
BufferedReader br;

if (responseCode >= 400) {
br = new BufferedReader(new InputStreamReader(conn.getErrorStream()));
} else {
br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
}

String response;
while ((response = br.readLine()) != null) {
responseBuilder.append(response);
}

//System.out.println("Código de resposta HTTP: " + responseCode);
//System.out.println("Resposta do servidor: " + responseBuilder);

JsonMapper mapper = JsonMapper
.builder()
.configure(MapperFeature.USE_ANNOTATIONS, false)
.build();

cob = mapper.readValue(responseBuilder.toString(), Cob.class);

conn.disconnect();
} catch (Exception e) {
e.printStackTrace();
}
return (cob != null) ? cob : new Cob();
}