# Multi-Remote Commanders จากโปรแกรม [`server.c`](/computer-operation-systems/linux-os-dev.-engineer/applied-ipc/remote-commander.md) ก่อนหน้านี้ ยังมีข้อจำกัดในการรองรับ client ที่เชื่อมต่อผ่าน socket เข้ามา จึงได้ปรับปรุงโปรแกรม server ให้สามารถรองรับการเชื่อมต่อจากตัว clients ได้หลายตัวพร้อมกันโดยใช้ความสามารถของ `pthread` ดังนี้ ```c // new_server.c #include #include #include #include #include #include #define PORT 8080 #define BUFFER_SIZE 1024 // Struct for arguments to pass to the thread handler typedef struct { int socket; } client_thread_args; // Function to execute the command and retrieve the output void execute_command(char* command, char* result, size_t result_size) { // Clear the result buffer memset(result, 0, result_size); FILE* pipe = popen(command, "r"); if (!pipe) { snprintf(result, result_size, "Error: failed to open pipe.\n"); return; } // Read command result into the buffer char buffer[128]; while (!feof(pipe)) { if (fgets(buffer, sizeof(buffer), pipe) != NULL) { strncat(result, buffer, result_size - strlen(result) - 1); } } pclose(pipe); } // Thread function to handle communication with a client void *client_handler(void *arg) { client_thread_args *args = (client_thread_args *)arg; int client_socket = args->socket; free(arg); // Free memory for arguments char buffer[BUFFER_SIZE] = {0}; char result[BUFFER_SIZE] = {0}; // Communication loop with the connected client while (1) { memset(buffer, 0, BUFFER_SIZE); // Clear the buffer int read_size = read(client_socket, buffer, BUFFER_SIZE); if (read_size > 0) { printf("Received command: %s\n", buffer); // Special case: close connection if client sends "exit" if (strcmp(buffer, "exit") == 0) { printf("Closing connection...\n"); close(client_socket); break; // Break out of the loop to end this thread } // Execute the command received from the client execute_command(buffer, result, BUFFER_SIZE); // Send back the result send(client_socket, result, strlen(result), 0); memset(result, 0, BUFFER_SIZE); // Clear the result buffer } else { printf("Client disconnected or read error...\n"); close(client_socket); break; // Break out of the loop to end this thread } } return NULL; // Thread ends here } int main(int argc, char const *argv[]) { int server_fd, new_socket; struct sockaddr_in address; int opt = 1; int addrlen = sizeof(address); // Creating socket file descriptor if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) { perror("socket failed"); exit(EXIT_FAILURE); } // Forcefully attaching socket to the PORT if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) { perror("setsockopt"); exit(EXIT_FAILURE); } address.sin_family = AF_INET; address.sin_addr.s_addr = INADDR_ANY; address.sin_port = htons(PORT); // Forcefully attaching socket to the PORT if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) { perror("bind failed"); exit(EXIT_FAILURE); } if (listen(server_fd, 3) < 0) { perror("listen"); exit(EXIT_FAILURE); } printf("Server started... Waiting for connections.\n"); // Main loop to keep server running and accepting new connections while (1) { if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) { perror("accept"); exit(EXIT_FAILURE); } printf("Connection established...\n"); // Create a thread for each client pthread_t client_thread; client_thread_args *args = (client_thread_args *)malloc(sizeof(*args)); args->socket = new_socket; if (pthread_create(&client_thread, NULL, client_handler, args) != 0) { perror("Could not create thread"); free(args); // Don't forget to free memory on failure close(new_socket); } else { pthread_detach(client_thread); // Automatically reclaim thread resources on exit } } return 0; // The server should never reach this part } ``` ทำการคอมไพล์โปรแกรมทั้งสอง โดยสร้างหน้าต่าง terminal จำนวน 3 หน้าต่าง ดังนี้ {% tabs %} {% tab title="หน้าต่าง Terminal ที่ 1" %} ```shell-session $ gcc -o new_server new_server.c -lpthread -Wall $ ./new_server Server is running at IP: 10.211.55.3 on Port: 8080 Connection established... Connection established... Received command: ls Result sent back to client. Received command: date Result sent back to client. Received command: ifconfig Result sent back to client. Received command: uname -a Result sent back to client. ``` {% endtab %} {% tab title="หน้าต่าง Terminal ที่ 2 - Client #1" %} ```shell-session $ gcc -Wall -o client client.c -lreadline $ ./client 10.211.55.3 8080 ─╯ shell> ls <------------- พิมพ์คำสั่งเพื่อส่งไปรันที่เครื่องปลายทาง Results from the remote machine [10.211.55.3]: client client.c new_server new_server.c other.c server server.c shell> ifconfig <------------- พิมพ์คำสั่งเพื่อส่งไปรันที่เครื่องปลายทาง Results from the remote machine [10.211.55.3]: docker0: flags=4099 mtu 1500 inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255 ether 02:42:88:82:fe:7b txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 enp0s5: flags=4163 mtu 1500 inet 10.211.55.3 netmask 255.255.255.0 broadcast 10.211.55.255 inet6 fe80::c7de:82d6:f3cc:96a0 prefixlen 64 scopeid 0x20 inet6 fd5c:edc7:dfd5:6910:6ea3:1b97:d393:2793 prefixlen 64 scopeid 0x0 inet6 fd5c:edc7:dfd5:6910:1956:adea:5a7b:c494 prefixlen 64 scopeid 0x0 ether 00:1c:42:8a:01:82 txqueuelen 1000 (Ethernet) RX packets 1908378 bytes 2334364363 (2.3 GB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 501740 bytes 57225273 (57.2 MB) TX errors 0 dropped 0 overruns ``` {% endtab %} {% tab title="หน้าต่าง Terminal ที่ 3 - Client #2" %} ```shell-session $ ./client 10.211.55.3 8080 ─╯ shell> date <------------- พิมพ์คำสั่งเพื่อส่งไปรันที่เครื่องปลายทาง Results from the remote machine [10.211.55.3]: อ. 24 ต.ค. 2566 14:09:43 +07 shell> uname -a <------------- พิมพ์คำสั่งเพื่อส่งไปรันที่เครื่องปลายทาง Results from the remote machine [10.211.55.3]: Linux wiroon-ubuntu 6.2.0-32-generic #32~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Aug 18 12:38:40 UTC 2 aarch64 aarch64 aarch64 GNU/Linux ``` {% endtab %} {% endtabs %} --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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