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--- linux:socket编程 [2023/02/07 15:10] – 创建 zhangguo
+++ linux:socket编程 [2023/03/17 10:12] (当前版本) – 外部编辑 127.0.0.1
@@ 行 1: / 行 1: @@
 ====== socket编程 ======
+===== - socket 学习 =====
+[[https://www.tutorialspoint.com/unix_sockets/socket_core_functions.htm|Unix Socket - Core Functions]]
+[[https://www.geeksforgeeks.org/socket-programming-cc/|Socket Programming in C/C++]]
+[[https://www.binarytides.com/socket-programming-c-linux-tutorial/|Socket programming in C on Linux – The Ultimate Guide for Beginners]]
+==== - 大图 ====
+{{:linux:pasted:20230221-092340.png}}
+{{:linux:pasted:20230221-085436.png}}
+=== - recv,read ===
+<code>
+Returns the number of bytes actually recieved (which might be less than you requested in the
+len paramter), or -1 on error (and errno will be set accordingly.)
+If the remote side has closed the connection, recv() will return 0. This is the normal method
+for determining if the remote side has closed the connection.
+</code>
+==== - function ====
+<code>
+. Socket creation:
+int sockfd = socket(domain, type, protocol)
+sockfd: socket descriptor, an integer (like a file-handle)
+domain: integer, specifies communication domain. We use AF_ LOCAL as defined in the POSIX standard for communication between processes on the same host. For communicating between processes on different hosts connected by IPV4, we use AF_INET and AF_I NET 6 for processes connected by IPV6.
+type: communication type
+SOCK_STREAM: TCP(reliable, connection oriented)
+SOCK_DGRAM: UDP(unreliable, connectionless)
+protocol: Protocol value for Internet Protocol(IP), which is 0. This is the same number which appears on protocol field in the IP header of a packet.(man protocols for more details)
+. Setsockopt:
+This helps in manipulating options for the socket referred by the file descriptor sockfd. This is completely optional, but it helps in reuse of address and port. Prevents error such as: “address already in use”.
+int setsockopt(int sockfd, int level, int optname,  const void *optval, socklen_t optlen);
+. Bind:
+int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
+After the creation of the socket, the bind function binds the socket to the address and port number specified in addr(custom data structure). In the example code, we bind the server to the localhost, hence we use INADDR_ANY to specify the IP address.
+. Listen:
+int listen(int sockfd, int backlog);
+It puts the server socket in a passive mode, where it waits for the client to approach the server to make a connection. The backlog, defines the maximum length to which the queue of pending connections for sockfd may grow. If a connection request arrives when the queue is full, the client may receive an error with an indication of ECONNREFUSED.
+. Accept:
+int new_socket= accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
+It extracts the first connection request on the queue of pending connections for the listening socket, sockfd, creates a new connected socket, and returns a new file descriptor referring to that socket. At this point, the connection is established between client and server, and they are ready to transfer data.
+Stages for Client
+Socket connection: Exactly same as that of server’s socket creation
+Connect: The connect() system call connects the socket referred to by the file descriptor sockfd to the address specified by addr. Server’s address and port is specified in addr.
+int connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
+Implementation
+Here we are exchanging one hello message between server and client to demonstrate the client/server model.
+Server.c
+// Server side C/C++ program to demonstrate Socket
+// programming
+#include <netinet/in.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+#define PORT 8080
+int main(int argc, char const* argv[])
+{
+    int server_fd, new_socket, valread;
+    struct sockaddr_in address;
+    int opt = 1;
+    int addrlen = sizeof(address);
+    char buffer[1024] = { 0 };
+    char* hello = "Hello from server";
+    // 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 8080
+    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 8080
+    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);
+    }
+    if ((new_socket
+         = accept(server_fd, (struct sockaddr*)&address,
+                  (socklen_t*)&addrlen))
+        < 0) {
+        perror("accept");
+        exit(EXIT_FAILURE);
+    }
+    valread = read(new_socket, buffer, 1024);
+    printf("%s\n", buffer);
+    send(new_socket, hello, strlen(hello), 0);
+    printf("Hello message sent\n");
+    // closing the connected socket
+    close(new_socket);
+    // closing the listening socket
+    shutdown(server_fd, SHUT_RDWR);
+    return 0;
+}
+client.c
+// Client side C/C++ program to demonstrate Socket
+// programming
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+#define PORT 8080
+int main(int argc, char const* argv[])
+{
+    int status, valread, client_fd;
+    struct sockaddr_in serv_addr;
+    char* hello = "Hello from client";
+    char buffer[1024] = { 0 };
+    if ((client_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
+        printf("\n Socket creation error \n");
+        return -1;
+    }
+    serv_addr.sin_family = AF_INET;
+    serv_addr.sin_port = htons(PORT);
+    // Convert IPv4 and IPv6 addresses from text to binary
+    // form
+    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr)
+        <= 0) {
+        printf(
+            "\nInvalid address/ Address not supported \n");
+        return -1;
+    }
+    if ((status
+         = connect(client_fd, (struct sockaddr*)&serv_addr,
+                   sizeof(serv_addr)))
+        < 0) {
+        printf("\nConnection Failed \n");
+        return -1;
+    }
+    send(client_fd, hello, strlen(hello), 0);
+    printf("Hello message sent\n");
+    valread = read(client_fd, buffer, 1024);
+    printf("%s\n", buffer);
+    // closing the connected socket
+    close(client_fd);
+    return 0;
+}
+Compiling:
+gcc client.c -o client
+gcc server.c -o server
+Output:
+Client:Hello message sent
+Hello from server
+Server:Hello from client
+Hello message sent
+Next: Socket Programming in C/C++: Handling multiple clients on server without multi threading
+This article is contributed by Akshat Sinha. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
+Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
+</code>
+===== - 示例代码 =====
 参考： https://blog.csdn.net/liranke/article/details/6079393/
 这个代码在linux系统下可直接使用，同样也适于xilinx zynq petalinx下使用。
+==== - 服务端代码 ====
-===== - 服务端代码 =====
 <code c>
@@ 行 90: / 行 294: @@
-===== - 客户端代码 =====
+==== - 客户端代码 ====
 <code c>