I have slight problem with programming an TCP client connection under Ethernet Shield. Let me show you simplified version of code: EthernetServer server = EthernetServer(23); void setup () { uint8_t macaddress[6] = {0x00, 0x0A, 0xB1, 0x54, 0xC7, 0xAA}; IPAddress localIP(192, 16…

If you use server.write, it does send the message to all connected clients. If you use client.write, it sends the message only to the active client. This is done with a private variable called _sock. If you want the equivalent of a telnet server, you must use the lower level parts of the ethernet …

You didn't understand me. I would like to know how to determine which "client" is active right now, because everyone of them is created inside of main loop, under the same name. Is it really necessary to use low-level functions, instead of typical Arduino Ethernet classes? What would happen, if I …

Is it really necessary to use low-level functions, instead of typical Arduino Ethernet classes? Yes, or modify the ethernet library to make _sock a public variable. Unfortunate but true. edit: It isn't as difficult to do with socket.h and w5100.h as you might think. I have some simple examples a…

I would be very grateful. :wink: Is there possibility of any conflict between my own function using socket.h and the rest of Ethernet Library? If I understand correctly, the main reason to do it your way, is allocation of only one socket for telnet server, without need of two objects: server and c…

Here is a test sketch for multiple active sockets. It doesn't store the entries for each socket, just displays them on the serial monitor. Change the network settings to your network. This is set to use port 80, but you can change that with the define. It should get you started. I'm not sure everyth…

Multiple TCP clients at the same time

Projects Networking, Protocols, and Devices

Topic		Replies	Views
Ethernet // EthernetServer , always take at least 2 sockets ? Networking, Protocols, and Devices	13	189	October 14, 2025
Server.write() in Ethernet library for arduino mega Networking, Protocols, and Devices	16	202	August 14, 2025
Connecting multiple clients to Arduino TCP/IP server Networking, Protocols, and Devices	7	11195	September 29, 2014
Ap only able to connected to 1 not 2 client at a same time Programming	6	699	December 20, 2022
TCP comms between arduinos Networking, Protocols, and Devices	16	234	March 12, 2026

Multiple TCP clients at the same time

Related topics