Question

我已经使用sctp协议编写了该服务器-客户端程序。当我在本地计算机上以环回IP作为目的地运行该程序时，该程序运行良好。但是，当我在两个不同的远程系统中运行服务器和客户端代码时，这些代码将无法正常工作。

sctp_sendmsg函数发送太多消息，发送成功后，我在服务器上看不到任何消息。

    /*
 * Compile:
 *
 *   gcc sctp.c -o server -lsctp -Wall
 *   ln -s server client
 *
 * Invoke:
 *
 *   ./client
 *   ./server
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <libgen.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
#include <arpa/inet.h>

#define MY_PORT_NUM 21233

static void die(const char *s) {
        perror(s);
        exit(1);
}

static void server(void) {
        int listen_fd, conn_fd, flags, ret, in;
        struct sctp_sndrcvinfo sndrcvinfo;
        struct sockaddr_in servaddr = {
                .sin_family = AF_INET,
                .sin_addr.s_addr = htonl(INADDR_ANY),
                .sin_port = htons(MY_PORT_NUM),
        };
        struct sockaddr_in client_addr;
        socklen_t clilen=sizeof(client_addr);
        struct sctp_initmsg initmsg = {
                .sinit_num_ostreams = 5,
                .sinit_max_instreams = 5,
                .sinit_max_attempts = 4,
        };

        listen_fd = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
        if (listen_fd < 0)
                die("socket");

        ret = bind(listen_fd, (struct sockaddr *) &servaddr, sizeof(servaddr));
        if (ret < 0)
                die("bind");


        ret = listen(listen_fd, initmsg.sinit_max_instreams);
        if (ret < 0)
                die("listen");

        for (;;) {
                char buffer[1024];

                printf("Waiting for connection\n");

                in = sctp_recvmsg(listen_fd, buffer, sizeof(buffer),(struct sockaddr*)&client_addr,&clilen,0,0);
                printf("%d\n",in);
                    if (in > 0) {
                            printf("Received data: %s\n", buffer);
                            fflush(stdout);
                    }
        }
        close(listen_fd);
}

static void client(void) {
        int conn_fd, ret;
        const char *msg = "Hello, Server!";
        struct sockaddr_in servaddr = {
                .sin_family = AF_INET,
                .sin_port = htons(MY_PORT_NUM),
                .sin_addr.s_addr = inet_addr("45.125.222.112"),
        };

        conn_fd = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
        if (conn_fd < 0)
                die("socket()");

        struct sctp_initmsg initmsg = {
                .sinit_num_ostreams = 5,
                .sinit_max_instreams = 5,
                .sinit_max_attempts = 4,
        };

        setsockopt(conn_fd, IPPROTO_SCTP, SCTP_INITMSG, &initmsg, sizeof(initmsg));
        int i;
        for(i=0;i<4;i++){
            printf("before sending\n");
            ret = sctp_sendmsg(conn_fd, (void *) msg, strlen(msg) + 1,(struct sockaddr*)&servaddr,sizeof(struct sockaddr),0,0,0,0,0);
            printf("after sending\n");
            if (ret < 0)
                    printf("failed to send %d\n",i);
            else 
                printf("success %d\n",i);

        }
        close(conn_fd);

}

int main(int argc, char **argv) {

        if (strstr(basename(argv[0]), "server"))
                server();
        else
                client();

        return 0;
}

Answer 1

您的客户端上没有连接呼叫。来自linux sctp man page：

典型的客户端使用以下系统调用序列来设置与服务器的关联以请求服务：

socket（）

connect（）

从connect（）返回后，客户端使用send（）和recv（）调用发出请求并从服务器接收响应。

基于sctp套接字的C服务器客户端程序

1 个答案: