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            ```Arduino
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            #include < | 
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              }
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| 1 | 
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            2022年4月現在で'ESP32 複数 クライアント'でググったらこれがトップでヒットしちゃって...ちょっと恥ずかしいかな。
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            普通にArduinoライブラリでもできちゃったので、一応そちらも載せておきます。二口分の受け方は「ベタ」に書いているので、実際になにかするなら美しくまとめてください。もちろん、動作中にreadStringUntil()とかでブロックしたりしちゃいけませんよ。
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            ```Arduino
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            #include <WiFi.h>
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            WiFiServer server(54321);
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            void setup() {
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                Serial.begin(115200);
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                WiFi.begin(); //引数省略で最後に接続したAPにつなぎに行く。WiFiの接続とソケットの接続を混同しないようにしましょう。
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                while (WiFi.status() != WL_CONNECTED) {
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                    delay(500);
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                }
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                Serial.println(WiFi.localIP());
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                server.begin();
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            }
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            WiFiClient client[2];
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            String s[2];
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            void loop() {
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              if( !client[0].connected()){
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                client[0]= server.available();
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                if(client[0].connected()){
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                  Serial.println("Connected to 0");
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                  client[0].println("Connected to 0");
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                }
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              }else{
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                while(client[0].available()){
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                  char c=client[0].read();
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                  s[0]+=c;
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                  if(c=='\n'){
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                    Serial.println(s[0]);
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                    client[0].print(s[0]);
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                  }
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                }
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              }
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              if( !client[1].connected()){
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                client[1]= server.available();
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                if(client[1].connected()){
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                  Serial.println("Connected to 1");
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                  client[1].println("Connected to 1");
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                }
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              }else{
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                while(client[1].available()){
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                  char c=client[1].read();
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                  s[1]+=c;
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                  if(c=='\n'){
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                    Serial.println(s[1]);
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                    client[1].print(s[1]);
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                  }
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                }
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              }
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            }
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            ```
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            以下原文
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            ---
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            既存のライブラリを真面目に探せばもっといい処理もできそうな気がしますが、見つからなかったので原始的にやってみました。WiFiを繋いだあとはCでソケットを扱う場合の定番にほぼ沿ったものです。
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            ```Arduino
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            #include <sys/select.h>
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            #include <sys/socket.h>
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            #include <WiFi.h>
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            static const char *WIFI_SSID = "WROOM32";
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            static const char *WIFI_PASS = "password";
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            const int port = 1337;
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            int fd, maxfd;
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            int fd2[2] = { -1, -1}; //二口だけ接続をうけつける
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            struct sockaddr_in addr;
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            struct sockaddr_in from_addr;
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            struct timeval tv;
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            //サーバー設定-------------------------------------------------
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            IPAddress ip(192, 168, 1, 10);
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            //-------------------------------------------------------------
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            void setup() {
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              Serial.begin(115200);
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              //Wi-Fiアクセスポイント開始--------------------------------------------------------
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              WiFi.mode(WIFI_AP);
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              WiFi.softAP(WIFI_SSID, WIFI_PASS);
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              WiFi.softAPConfig(ip, WiFi.gatewayIP(), WiFi.subnetMask());
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              //WiFi.softAPConfig(ip, gateway, netmask);
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              IPAddress myIP = WiFi.softAPIP();
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              Serial.println("APStarted. myIP Address:");
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              Serial.println(myIP);
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              Serial.print("server Mac Address: ");
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              Serial.println(WiFi.macAddress());
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              Serial.print("Subnet Mask: ");
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              Serial.println(WiFi.subnetMask());
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              Serial.print("Gateway IP: ");
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              Serial.println(WiFi.gatewayIP());
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              //------------------------------------------------------------------------------
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              if ( (fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
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                Serial.println("socket error.");
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                while (1);
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              }
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              addr.sin_family = AF_INET;
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              addr.sin_port = ntohs(port);
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              addr.sin_addr.s_addr = INADDR_ANY;
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              if ( bind( fd, (struct sockaddr *)&addr, sizeof(addr)) < 0 ) {
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                Serial.println( "bind error" );
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                while (1);
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              }
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            }
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            void loop() {
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              if ( listen(fd, 1) < 0) {
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                Serial.println("listen error.");
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              }
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              fd_set fds;
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              FD_ZERO(&fds);
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              FD_SET( fd, &fds);
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              maxfd = fd;
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              for (int i = 0; i < 2; i++) {
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                if (fd2[i] != -1) {
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                  FD_SET(fd2[i], &fds);
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                  if (fd2[i] > fd) {
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                    maxfd = fd2[i];
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                  }
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                }
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              }
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              tv.tv_sec = 0;
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              tv.tv_usec = 10000;
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              int cnt = select(maxfd + 1, &fds, NULL, NULL, &tv);
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              if (cnt <= 0) {
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                //error or timeout
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                for (int i = 0; i < 2; i++) {
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                  if (fd2[i] >= 0) {
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                  //既接続のソケットに対して送信
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                    char buf[32];
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                    cnt = sprintf(buf, "To %d %ld\n", fd2[i], millis());
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                    write(fd2[i], buf, cnt);
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                  }
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                }
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              }
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              if (FD_ISSET( fd, &fds)) {
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                for (int i = 0; i < 2; i++) {
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                  //接続受付
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                  if (fd2[i] == -1) {
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                    socklen_t len = sizeof(struct sockaddr_in);
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                    if ((fd2[i] = accept(fd, (struct sockaddr *)&from_addr, &len)) < 0) {
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                      Serial.println("accept error.");
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                      while (1);
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                    }
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                    Serial.println("connect " + String( fd2[i]));
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                    break;
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                  }
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                }
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              }
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              for (int i = 0; i < 2; i++) {
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                if (fd2[i] != -1 && FD_ISSET(fd2[i], &fds) ) {
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                  //受信&接続断検出
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                  char buf[256];
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                  int rcvCnt = recv(fd2[i], buf, sizeof(buf), 0);
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                  Serial.println("rcvd:" + String(buf));
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                  if (rcvCnt < 0) {
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                    Serial.println("disconnect " + String(fd2[i]));
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                    close(fd2[i]);
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                    fd2[i] = -1;
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                  }
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                }
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              }
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            }
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            ```
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