Finish the test

.gitignore

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+/bin

Makefile

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+CC=gcc
+CC_OPTIONS=-shared-libgcc
+
+CLIENT_SOURCE=src/client.c
+SERVER_SOURCE=src/server.c src/myutil.c
+
+.PHONY: all
+all: bin/client bin/server
+	
+.PHONY: clean
+clean:
+	rm -r bin
+
+bin/client: $(CLIENT_SOURCE)
+	[[ -d bin ]] || mkdir bin
+	$(CC) $(CC_OPTIONS) -o bin/client $(CLIENT_SOURCE)
+
+bin/server: $(SERVER_SOURCE)
+	[[ -d bin ]] || mkdir bin
+	$(CC) $(CC_OPTIONS) -o bin/server $(SERVER_SOURCE)

README

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+# Test Buffer For Udp
+
+This project is used to test if there is a buffer for udp. Let's assume packet
+A and B are sent orderly in the same time, the receiver can still read A after
+B already arrive, then we think the buffer for udp is exists.
+
+## Program behavier
+
+Server listen on port 23333, receive 1 packet, then sleep for 1 second,
+and receive the remain 2 packets, then exit.
+
+Client send 3 packet to 127.0.0.1:23333 without delay.
+
+## Expected result
+
+The expected result is server receive the frst packet at the moment the client
+launch, then 1 second later, the server receive the remain 2 packets with no
+interval. And the client launch and exit in a very short time.
+
+## Run the program
+
+To run the program, first build the program
+
+    make
+
+then launch server
+
+    ./bin/server
+
+then launch client in another terminal
+
+    ./bin/client
+
+Or if you want one line command
+
+    make ; ./bin/server & ; pid=$! ; ./bin/client ; wait $pid

src/client.c

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+#include <sys/socket.h>
+#include <sys/types.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int main() {
+    struct addrinfo hints;
+    struct addrinfo * result;
+
+    memset(&hints, 0, sizeof(struct addrinfo));
+    hints.ai_family = AF_INET;
+    hints.ai_socktype = SOCK_DGRAM;
+    hints.ai_protocol = 0;
+    hints.ai_flags = AI_PASSIVE;
+    hints.ai_addr = NULL;
+    hints.ai_next = NULL;
+
+    int err = getaddrinfo("127.0.0.1", "23333", &hints, &result);
+    if (err != 0) {
+        fprintf(stderr, "getaddrinfo failed: %s\n", gai_strerror(err));
+        exit(EXIT_FAILURE);
+    }
+
+    int sock_fd;
+    struct addrinfo * i;
+    for (i = result; i != NULL; i = i->ai_next) {
+        sock_fd = socket(i->ai_family, i->ai_socktype, i->ai_protocol);
+        if (sock_fd == -1)
+            continue;
+
+        if (connect(sock_fd, i->ai_addr, i->ai_addrlen) != -1)
+            break;
+
+        close(sock_fd);
+    }
+
+    freeaddrinfo(result);
+
+    if (i == NULL) {
+        fprintf(stderr, "Could not connect\n");
+        exit(EXIT_FAILURE);
+    }
+
+    char x = 1;
+    send(sock_fd, &x, 1, 0); x++;
+    send(sock_fd, &x, 1, 0); x++;
+    send(sock_fd, &x, 1, 0); x++;
+
+    close(sock_fd);
+
+    return EXIT_SUCCESS;
+}

src/myutil.c

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+#include "myutil.h"
+#include <stdio.h>
+
+void print_buffer(FILE * stream, const char *const buffer, size_t len) {
+    for (size_t i = 0; i < len; i++) {
+        if (i != 0)
+            fprintf(stream, " ");
+        fprintf(stream, "%2x", buffer[i]);
+    }
+}

src/myutil.h

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+#include <stdio.h>
+
+void print_buffer(FILE* stream, char const * const buffer, size_t len);

src/server.c

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+#include <sys/socket.h>
+#include <sys/types.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "myutil.h"
+
+int main() {
+    struct addrinfo hints;
+    memset(&hints, 0, sizeof(struct addrinfo));
+    hints.ai_family = AF_INET;
+    hints.ai_socktype = SOCK_DGRAM;
+    hints.ai_protocol = 0;
+    hints.ai_flags = AI_PASSIVE;
+    hints.ai_addr = NULL;
+    hints.ai_next = NULL;
+
+    struct addrinfo *result;
+    int err = getaddrinfo(NULL, "23333", &hints, &result);
+    if (err != 0) {
+        fprintf(stderr, "getaddrinfo failed: %s\n", gai_strerror(err));
+        exit(EXIT_FAILURE);
+    }
+
+    int sock_fd;
+    struct addrinfo * i;
+    for (i = result; i != NULL; i = i->ai_next) {
+        sock_fd = socket(i->ai_family, i->ai_socktype, i->ai_protocol);
+        if (sock_fd == -1)
+            continue;
+
+        if (bind(sock_fd, i->ai_addr, i->ai_addrlen) == 0)
+            break;
+    }
+
+    freeaddrinfo(result);
+
+    if (i == NULL) {
+        fprintf(stderr, "Could not bind\n");
+        exit(EXIT_FAILURE);
+    }
+
+    size_t BUF_SIZE = 1024;
+    char buffer[BUF_SIZE];
+    struct sockaddr_storage peer_addr;
+    socklen_t peer_addr_len = sizeof(struct sockaddr_storage);
+
+    for (int i = 0; i < 3; i++) {
+        if (i == 1)
+            sleep(1);
+        ssize_t nread = recvfrom(
+            sock_fd, buffer, BUF_SIZE, 0, (struct sockaddr *)&peer_addr, &peer_addr_len
+        );
+
+        fprintf(stdout, "read %ld bytes: ", nread);
+        print_buffer(stdout, buffer, nread);
+        fprintf(stdout, "\n");
+    }
+
+    return EXIT_SUCCESS;
+}